CHIANG RAI – Ongoing reports of contamination in northern rivers are raising fresh concern in Northern Thailand. Tests have repeatedly found pollutants in the Sai River, Kok River, Ruak River, and parts of the Mekong in Chiang Rai and Chiang Mai.
Many observers suspect mining activity across the border in Shan State, Myanmar, may be linked, especially as large amounts of minerals continue to move into Thailand and are later exported.
Thailand’s Pollution Control Department has been monitoring these waterways about once every two months. In its 14th round of sampling (December 9 to 12, 2025), it reported:
- Sai River: arsenic measured 0.011 to 0.014 mg/L, above the Thai standard
- Ruak River: copper measured 0.154 mg/L near the Koh Chang water pumping station, also above the standard
- Other sampling points showed substances within the standard limits
These findings have kept attention on mines near rivers in Myanmar, and on the supply chain that moves minerals through Thai border checkpoints and out through Thai ports.
Mineral imports through multiple border points
According to information cited from the Customs Department, Thailand imported large amounts of minerals from Myanmar between 2022 and 2025, including shipments through the Chiang Saen Customs House in Chiang Rai.
Ferrosilicomanganese imports via Chiang Saen (Chiang Rai)
- 2022: 1.7 tons, 39.3 million baht
- 2023: 4.1 tons, 133.8 million baht
- 2024: 4.6 tons, 151.3 million baht
- 2025: 1.7 tons, 58.3 million baht
Manganese ore was also imported, with 10,925 tons recorded in 2022.
Manganese ore has been imported for years, across several checkpoints
The report says manganese ore has been imported from 2016 to 2025 by 41 private companies. Some firms reportedly brought in more than 20,000 to 30,000 tons per year, often through the Mae Sai checkpoint in Chiang Rai.
Imports also entered through other crossings, including:
- Mae Sot (Tak)
- Sangkhla Buri (Kanchanaburi)
- Mae Sariang (Mae Hong Son)
Lead, copper, and tungsten also appear in the import record
For 2025, lead imports were reported at a value of 940.6 million baht, with most entering through Mae Sot. Smaller volumes of copper and tungsten were also mentioned.
A major spike in Ore Concentrate
The biggest import category in the report is ore concentrate, especially in 2025 (first 9 months). It states that 88 private companies were involved.
At Mae Sot, one importer alone reportedly brought in 59,265.5 tons, valued at 2,558.8 million baht. Another importer reportedly brought in 28,847.3 tons, with other firms following behind.
Overall, in 2025, Thailand reportedly imported ore concentrate mostly via Mae Sot, totaling:
- 106,289.1 tons, worth 5,729.7 million baht
The same year also recorded imports of unprocessed ore concentrate totaling:
- 4,253.7 tons, worth 7,170.2 million baht
Minerals reportedly shipped out via Laem Chabang to China
The report highlights that ferrosilicomanganese, manganese ore, and ore concentrate were exported in large quantities through Laem Chabang Port in Chonburi, especially ore concentrate.
For 2025, when combining Laem Chabang with other export points, ore concentrate exports were reported at:
- 39,593.17 tons, worth 3,260.78 million baht
It also states that shipments leaving Laem Chabang by cargo vessel were ultimately headed to buyers in China.
Report points to Chinese investment at the mine source
The supply chain described in the report includes several groups:
- Mine sites in Myanmar sites, where Chinese investors are said to be involved from the start
- Local power holders in mining areas, including armed ethnic groups in Shan State (such as Wa and Kokang), and in some areas connected to the Myanmar military
- Transport and logistics operators, described as private firms that bring minerals through Thailand and move them to Laem Chabang
- End buyers in China, possibly linked to the same groups investing at the mine sites
Local impacts and river concerns in border areas
The report claims many groups profit from mining, while communities downstream face the risks. It describes examples such as:
- In Mae Sot, two importers reportedly set up warehouses near the river, raising concern about possible waste discharge into the Moei River
- At the headwaters of the Sai River and Kok River, mining activity in Myanmar is said to be visible from the Thai side in some areas, including viewpoints from mountainous parts of Mae Fah Luang District, Chiang Rai
Dr. Suebsakul Kitnukul, a lecturer in the School of Social Innovation at Mae Fah Luang University, said past talks with Myanmar have not produced real progress.
He explained that when Thailand reported arsenic above 0.01 mg/L in the Sai River, Myanmar’s side responded that its standard is 0.05 mg/L. He also noted that some locations are difficult for Myanmar authorities to access because they are controlled by armed ethnic groups. As a result, discussions have not led to clear fixes.
He proposed that Thailand apply pressure to form a joint committee and use traceability checks across the whole chain, from mining sites to transport routes through Myanmar and Thailand, and onward to the final market in China.
He also said Thailand still lacks clear information on how many mines operate along riverbanks, what types they are, and which sites may be causing pollution. With a joint mechanism, he argued, it would be easier to identify problematic mines and block imports from those sources.
In his view, the leading benefits flow to local power holders at the source, transport operators moving goods through Thailand, and buyers in China, while people living along the river basins in Thailand see little benefit and bear the pollution risks instead.
