The clash took place on the ridge of Doi Sam Sao on the border of Thailand and Myanmar near Ban Loyo in tambon Patueng of Chiang Rai's Mae Chan district opposite a drug production plant of the United Wa State Army, or Red Wa, in the vicinity of Muong Yon in Myanmar.
The rangers from Company 3108 and Company 3109 under Task Force 31 were despatched to lie in wait in the area on receiving information that a band of drug traffickers of the UWSA under Lt Col Yise would transport drugs across the border via Doi Sam Sao.
On Sunday morning, the rangers spotted eight armed traffickers and stopped them for a search. The traffickers opened fire and an exchange of fire ensued for about two hours. During the clash, the rangers detonated claymore mines planted in the area.
The traffickers retreated across the border.
Later, while checking the clash site, the rangers found four bodies in a shallow creek.
They recovered from the bodies 25 bundles of 50,000 methamphetamine pills, 13 packs of heroin weighing about 2kg, one AK47 rifle, one shotgun, and one Chinese-made hand grenade.
On receiving a report on the clash, Pol Maj Gen Wanchai Suwansirikhet, the Chiang Rai police chief, and Col Yongyuth Laokhetkan, commander of a task force of the Pha Muang Force, rushed to the scene.