A Thai army Black Hawk helicopter with nine people aboard, including the commander of the Kanchanaburi-based 9th Infantry Division, is missing and believed to have crashed near the Burmese border on Tuesday.
The fate of the nine passengers was still not known.
Col Sansern Kaewkamnerd, the army spokesman, said the helicopter was on a mission to retrieve the bodies of soldiers killed when another helicopter crashed in Kaeng Krachan National Park in Suan Phung district of Phetchaburi province on Saturday.
Reports said the Black Hawk departed an air base in Kaeng Krachan district about 11.30am, heading to Kaeng Krachan park, which is on the border with Burma.
On board were Maj-Gen Tawan Ruangsri, the 9th Infantry Division chief and commander of the Surasee Task Force, Maj Prapan Jiamsoongnoen, the 1st pilot, Maj Chuphan Polwan, the 2nd pilot, Sgt-Maj Somkid Wongtoksaeng, the senior flight mechanic, Sgt Aram Wongsing, the second mechanic, Capt Jate Sudchai, Capt Chakraphan Bamrungphuet, L-Cpl Itthisak Hinasuthi, and Sornwichai Kongtannukul, a TV Channel five cameraman.
The Black Hawk was accompanied by helicopters. was a Natural Resource and Surroundings Ministry helicopter with Chaiwat Limlikit-aksorn, chief of the Kaeng Krachan National Park, and officials on board. The other was a helicopter operated by the Agriculture and Cooperatives Ministry.
The helicopters were flying about one,100 metres above mean sea level and were approaching the landing zone where the bodies of the army men were to be picked up when the weather suddenly turned bad.
Dark clouds moved in, cloaking the area, and rain began to fall.
Only the army Black Hawk proceeded to the target landing zone in the national park.
The helicopters operated by of the Natural Resources and Surroundings and Agriculture ministries decided to turned back and land at separate landing pads in the vicinity.
About 11.55am all radio contact with the Black Hawk suddenly ceased.
A radio centre at a place called Ton Nam Phet reported that a loud explosion was heard from a spot near where the first helicopter crashed on Saturday.
The centre reported that the Black Hawk was believed to have crashed in to the mountain which claimed the first helicopter on Saturday, possibly 1-2 kilometres on the Burmese side of the border.
Deputy Prime Minister Suthep Thaugsuban, in charge of security affairs, said army chief Gen Prayuth Chan-ocha reported to him that it was not yet clear whether the feasible crash site was in Thailand or Burma.