BANGKOK – The Thailand-Cambodia dispute matters because unresolved land claims and competing maritime claims in the Gulf of Thailand touch national identity, offshore energy, and regional stability. As of November 2026, neither the wider border questions nor the sea claims have a final settlement.
The land and maritime disputes are linked by strained relations, but they have different histories and legal processes. The ICJ has ruled on the Temple of Preah Vihear and its promontory, while the Gulf claims remain unresolved after Thailand withdrew from the 2001 maritime memorandum in May 2026. This guide explains what those decisions and agreements cover, what they leave open, and how diplomacy may help limit further tension.
Key Takeaways
- Thailand and Cambodia face separate disputes over their land border and overlapping claims in the Gulf of Thailand; neither has a final settlement.
- The ICJ confirmed Cambodia’s sovereignty over Preah Vihear and its promontory, but left nearby boundary sections to bilateral talks, as its rulings explain.
- The 2000 land-boundary memorandum supports demarcation, while the fragile December 2025 ceasefire and ASEAN monitoring address security, not sovereignty.
- Thailand’s May 2026 withdrawal from the 2001 maritime memorandum ended that negotiation framework, but did not settle Gulf boundaries or offshore resource rights.
- Cambodia’s UNCLOS conciliation offers a separate process, and both maritime claims remain unresolved, as outlined in coverage of the Gulf dispute.
What the territorial and maritime conflict between Thailand and Cambodia is about
Thailand and Cambodia have two distinct disputes: an approximately 800-kilometer land frontier with unresolved sections, and overlapping claims to maritime zones in the Gulf of Thailand. National identity and access to potential offshore resources raise the stakes, but the disputes follow different legal paths.
Why the border is still disputed
The frontier’s length does not mean every part is contested. Some sections have an agreed legal boundary, while others remain disputed or still need to be marked on the ground. These terms describe different problems.
A recognized border is a boundary both countries accept as legally established. A disputed area is territory where they disagree about which country has sovereignty. A boundary that needs to be marked, or demarcated, may have a legal basis but lack agreed markers or a precise on-the-ground line.
The 1962 International Court of Justice (ICJ) ruling awarded the Temple of Preah Vihear to Cambodia. In 2013, the Court clarified that Cambodia also held sovereignty over the temple’s promontory. However, those decisions did not define every nearby section of the frontier or settle all other border claims. The ICJ’s Preah Vihear case record covers the temple dispute, while the countries’ 2000 land-boundary memorandum provides a separate framework for demarcation. Both countries still need to address unresolved sections through bilateral processes.
How the land and sea disputes differ
Preah Vihear concerns sovereignty over land and where the international boundary runs. The Gulf dispute concerns maritime zones, the areas at sea where a country may exercise rights over waters, the seabed, and resources. Those zones overlap because Thailand and Cambodia claim some of the same waters and seabed.
The countries’ 2001 maritime memorandum set up a framework to discuss both boundary delimitation and possible joint development of offshore oil and gas. It did not create a final maritime boundary or a resource-sharing agreement. Thailand withdrew from that memorandum in May 2026, and the competing Gulf claims remain unresolved. The Gulf of Thailand dispute and potential gas reserves explain why the overlap has economic as well as political weight.
The two disputes are connected by strained relations and nationalist pressure, but one ruling or agreement cannot settle both. A land decision addresses territory on the frontier; maritime negotiations concern rights at sea and access to possible energy resources.
How Preah Vihear became the best-known land dispute
Preah Vihear became the best-known flashpoint on the Thailand-Cambodia border because a colonial-era map, competing readings of a treaty, and two International Court of Justice (ICJ) rulings made the temple dispute a test of sovereignty. The court resolved who owns the temple and its promontory, but it did not settle every nearby boundary claim.
The 1904 treaty, the map, and the 1962 ICJ ruling
The dispute’s modern roots lie in the 1904 treaty between France, which then controlled Cambodia, and Siam, now Thailand. It set the boundary near Preah Vihear along the watershed in the Dângrêk Mountains. A map produced after the treaty’s boundary work placed the temple on the Cambodian side, although the line shown there did not follow the watershed as Thailand later argued it should.
In 1962, the ICJ considered the map alongside the countries’ actions over time. The court found that Thailand had accepted the map and ruled that the Temple of Preah Vihear was in Cambodian territory. It ordered Thailand to withdraw military or police forces stationed at the temple or in its vicinity on Cambodian territory, and to return objects removed from the ruins since 1954. The ICJ case record summarizes the judgment and its orders.
The ruling addressed sovereignty over the temple, not every stretch of the border nearby. That distinction became central as the two countries disputed how far the decision extended beyond the temple itself.
What the 2013 ruling clarified, and what it left open
Cambodia asked the ICJ to interpret its 1962 judgment after disagreements over the territory covered by the ruling. In 2013, the court concluded that the earlier judgment recognized Cambodia’s sovereignty over the whole Preah Vihear promontory, the elevated area on which the temple stands. Thailand was required to withdraw its forces from that territory.
However, the court did not define the complete boundary in surrounding areas or decide sovereignty over every nearby location. Its interpretation concerned the promontory, not all disputed sections of the frontier. The 2013 judgment sets out both the scope of the ruling and its limits.
Why the 2000 land-boundary agreement has not finished the job
The 2000 memorandum of understanding created a bilateral process for surveying and demarcating the land border. It is separate from the 2001 memorandum on maritime claims in the Gulf of Thailand. Having a process in place, however, does not mean both governments agree on the boundary or have completed its demarcation.
Some sections remain unresolved, while disagreements over how to interpret maps and treaties complicate progress. The 2000 framework has not settled those claims, and the ICJ’s decisions covered only the temple and its promontory. The 2000 land-boundary memorandum and stalled talks provide context for why the broader border question remains open.
What the Gulf of Thailand maritime dispute means for energy
The Gulf dispute combines competing claims to sea territory with the question of who can explore for offshore oil and gas. The potential resources raise the economic stakes, but they remain estimates, and no agreement currently gives either country the right to develop them jointly.
The overlapping claims area and its potential resources
Thailand and Cambodia claim maritime zones that overlap across roughly 27,000 square kilometers in the Gulf of Thailand. The dispute involves rights over the seabed and its resources, including areas where offshore energy exploration could take place.
Recent analyses estimate that the contested area may contain about 1.6 billion barrels of oil and 17 trillion cubic feet of natural gas. These figures describe possible resources, not confirmed, commercially recoverable reserves. Exploration and production would require investment, technical work, and a settled legal framework.
Any future development could matter to both countries’ energy supplies and government revenues. Thailand relies heavily on natural gas for power generation, while Cambodia could gain access to new domestic energy resources. But until the parties agree on boundaries or a way to share development, the estimates remain potential value rather than an operating energy project. For context, Thailand’s dependence on domestic natural gas adds to the interest in offshore supply.
What the 2001 memorandum was designed to do
The 2001 memorandum proposed two sets of negotiations at the same time. In one area, the countries would work toward a joint-development arrangement for hydrocarbons. In another, they would negotiate a mutually acceptable maritime boundary.
A Joint Technical Committee was meant to help develop the terms, including a basis for sharing the costs and benefits of resource development. The memorandum, often called MOU 44, established a negotiating framework. It did not create a completed resource-sharing deal, authorize production, or draw a final border. As the memorandum’s history and negotiations show, the countries had not reached the proposed agreements before the framework ended.
Why the maritime talks changed in 2026
On May 5, 2026, Thailand formally approved withdrawal from the memorandum, citing a lack of progress. The decision came amid worsening bilateral relations after the land-border conflict and growing nationalist pressure. It removed the existing bilateral framework for negotiating joint energy development and maritime delimitation.
However, withdrawal did not settle the competing claims or transfer rights to the resources. Cambodia initiated compulsory conciliation under Annex V of the United Nations Convention on the Law of the Sea (UNCLOS), opening a separate process. The UNCLOS conciliation proceedings offered another channel for addressing the dispute, but no outcome had resolved the claims as of November 2026. The countries still face the underlying question: whether they can agree on a boundary, a resource-sharing arrangement, or both.
How border clashes led to the fragile 2025-26 ceasefire
The ceasefire followed decades of tension around disputed sections of the land border, then two rounds of fighting in 2025. Each truce stopped active clashes for a time, but neither settled the territorial claims or removed the risk of renewed violence.
From the 2008-2011 fighting to the 2025 escalation
Disputes over Preah Vihear and nearby territory contributed to clashes between 2008 and 2011. The fighting caused deaths on both sides, displaced Cambodian villagers, and damaged the temple. Although the International Court of Justice ruled on the temple and its promontory, it did not settle every nearby boundary question.
Tensions rose sharply again in 2025. After a deadly May border skirmish, the countries exchanged accusations and military measures. Fighting erupted in late July and continued for five days before a ceasefire took effect. Reporting at the time said at least 38 people were killed and more than 300,000 people left their homes. The July ceasefire agreement halted the immediate violence, but the pause did not last.
On October 26, Thailand and Cambodia signed another accord in Kuala Lumpur. It also failed to hold: the agreement broke down in early December as tensions and allegations of violations mounted. That sequence showed how quickly a truce could unravel when the underlying border disagreements remained unresolved.
What happened during the December fighting
The second round began on December 8, 2025, and lasted 20 days. The fighting was more prolonged than the July clashes, with civilians caught in border areas as military operations intensified. According to reporting on the conflict, at least 101 people were killed, while roughly one million people on both sides were displaced. Those figures are reported estimates, not a final accounting.
Thailand and Cambodia signed a new ceasefire on December 27. Reuters reported on the agreement as the two governments sought to stop weeks of intense fighting. China and ASEAN supported the effort, and subsequent peace talks focused on keeping the truce in place.
What the ceasefire does, and why it remains under strain
The December 27 agreement is intended to prevent a return to fighting, not resolve who owns disputed territory. It provides for ASEAN observers in both countries and commits the governments not to reinforce border positions or take provocative action. The Crisis Group’s account of the ceasefire describes these measures as part of efforts to reduce the risk of renewed clashes.
Military representatives met on October 28, 2026, to discuss implementation. Still, mutual accusations and nationalist pressure continue to strain the truce, while border checkpoints remain closed. The December agreement has helped contain violence, but it has not settled sovereignty claims or completed border demarcation. As of November 2026, it remains a fragile ceasefire, not a lasting settlement.
Which diplomatic paths could reduce tensions
Thailand and Cambodia have several channels available, but each has a different job. Court rulings address defined legal questions, bilateral mechanisms can work on unresolved boundaries, and regional observers can help prevent a ceasefire from collapsing. The maritime conciliation process offers another forum for discussion, but it does not automatically settle competing claims.
What courts and agreements can decide
The International Court of Justice (ICJ) ruled that the Temple of Preah Vihear belongs to Cambodia. In 2013, it clarified that Cambodia also holds sovereignty over the temple’s promontory. Those rulings resolve the questions they addressed, but they do not draw every adjoining section of the border. The ICJ’s interpretation of the Preah Vihear judgment helps explain why nearby demarcation remains a separate issue.
For those unresolved sections, the countries must rely on bilateral work. Their 2000 land-boundary memorandum provides a framework for surveying and demarcation, but it does not impose a final settlement on every disputed stretch. The governments still need to agree on how to apply that framework and resolve differences over the line.
The distinction matters: the ICJ has ruled on the temple and promontory, while bilateral negotiations and the land-boundary process address work left open beyond them.
How ASEAN and outside partners can help
ASEAN observers can monitor the December 2025 ceasefire and report on implementation. China has also supported ceasefire efforts. Neither ASEAN nor China decides sovereignty or replaces negotiations between the two governments.
Monitoring can reduce the chance that an incident or conflicting account triggers another escalation. In addition, direct communication between military representatives can help clarify events near the border before either side responds with force. Verification gives both governments a shared basis for discussing alleged violations, even when they disagree about the underlying territorial claims. The fragile ceasefire and its monitoring challenges show why maintaining these channels matters.
What UNCLOS conciliation may contribute
Cambodia’s Annex V conciliation under the United Nations Convention on the Law of the Sea (UNCLOS) concerns the maritime dispute in the Gulf of Thailand. In plain terms, conciliation gives the parties a diplomatic-legal process to present their positions and seek a negotiated way forward with help from a commission. It is separate from the land-boundary framework and the ICJ’s rulings on Preah Vihear.
However, conciliation does not automatically establish a maritime boundary or settle claims to offshore resources. Thailand’s withdrawal from the 2001 maritime memorandum ended that framework, but it did not resolve the overlapping claims. The UNCLOS process concerning the Gulf dispute could support further discussion; its outcome was not established in available reporting by November 2026.
Frequently Asked Questions
These answers clarify what the court decisions, diplomatic agreements, and ceasefire do and do not cover. The key distinction is between managing disputes and reaching a final settlement.
Did the ICJ award all disputed land to Cambodia?
No. The ICJ ruled that the Temple of Preah Vihear belongs to Cambodia, then clarified Cambodia’s sovereignty over the temple’s promontory in 2013. It did not settle every section of the surrounding land boundary, as the Court’s case summary explains.
Does Thailand’s withdrawal from the 2001 memorandum settle the sea boundary?
No. Thailand’s withdrawal in May 2026 ended the memorandum’s role as the bilateral framework for maritime talks, but it did not resolve the overlapping claims or establish a final boundary. Cambodia’s separate UNCLOS approach to maritime claims also does not, by itself, settle the dispute.
Are the Thai-Cambodian border crossings open?
Reporting available through November 2026 described the checkpoints as closed since June 2025. That reporting did not establish a later reopening, so the status should not be assumed to have changed.
Is the December 2025 ceasefire a peace agreement?
No. The December 27 ceasefire is intended to stop fighting and support monitoring, including through ASEAN observers. It is not a final peace treaty and does not settle land or maritime claims.
Why do oil and gas matter to the maritime dispute?
Estimated oil and gas resources could bring substantial economic benefits to both countries. However, extraction would depend on agreement over competing claims and boundaries, as well as how development costs and revenues would be shared.
