Thailand and Cambodia have boosted their military presence at a disputed border crossing in Ubon Ratchathani's Nam Yuen district after Cambodian authorities moved in equipment to begin work on a development project in an area claimed by both countries.
Thailand ordered the Chong Arn Ma temporary border pass shut down after Cambodian authorities brought in heavy machinery to excavate the area considered to be a watershed line.
Ubon Ratchathani governor Serm Chainarong said Tuesday he had sent a letter of protest to Preah Vihear governor Oam Mara, informing him that the Cambodian authorities were violating an agreement on a border survey and land demarcations.
It appeared Tuesday that Cambodian military officials had contacted their Thai counterparts and given assurances they would cease the construction work, according to a source.
Mr Serm said the Cambodians had hauled in backhoes and heavy machinery to work on an area around a monument to a Cambodian warrior on horseback at a Cambodian community market. The excavation is part of a project to build a casino and a hotel, develop the market, and expand roads.
Mr Serm said Cambodian residents are set to move into the area after the construction is completed. But Mr Serm called the area a "no man's land".
Ubon Ratchathani governor Serm Chainarong, second right, inspects the Chong Arn Ma temporary border pass in Nam Yuen district. Thailand and Cambodia have boosted their military presence there following a dispute. (Photo by Thaweesak Butchan)
The boundary line in the area is unclear and if Cambodian authorities change the original landscape, attempts to demarcate the border will be frustrated, he said.
Mr Serm said the Cambodian move is a violation of Thai territory and threatens to affect relations between the two countries.
He demanded Cambodia stop the work immediately.
He said he will raise the issue at a joint meeting between Thai and Cambodia officials. Cambodia should return the excavated area to its original state, Mr Serm said.
On Sept 27, a delegation of Thai local officials, led by the Ubon Ratchathani governor, met the Preah Vihear governor in Preah Vihear province to discuss border cooperation issues.
One of the conclusions reached was that Cambodia would relocate the market from the undemarcated area to a new location, said a source who was present at the discussion.
Cambodia's move to excavate land appears to be a violation of the agreement, which the source said has upset the Thai side.
In response, Ubon Ratchathani ordered the closure of the temporary border pass on Monday morning, the source said.
A military source said Cambodia began to funnel more soldiers and weapons to the Chong Arn Ma pass on Monday night, while Cambodia evacuated civilians from the market. It is unclear how many troops are now stationed in the area.
Thai reinforcements from the 6th Infantry Regiment's Sappasitthiprasong camp have been deployed to support troops already stationed at the border pass.
The source said Lt Gen Srai Duk, who is in charge of the Cambodian troops, has contacted the military commander on the Thai side about reopening the crossing.
Cambodia has promised to stop the digging work and called for talks to end the standoff, the source said.
Speaking after a cabinet meeting Tuesday, the deputy government spokesman, Maj Gen Sansern Kaewkamnerd, said Prime Minister Prayut Chan-o-cha had stressed that demarcation of border areas must be carried out with sincerity.
Demarcation can proceed straight away in areas that have clear boundaries, Maj Gen Sansern said. "In cases of unclear boundaries, neighbouring countries should give more attention to projects that develop border trade and share benefits, rather than fight over border lines," Maj Gen Sansern quoted Gen Prayut as saying.