Jinana Samsri, chief of Phu Jong Na Yoi National Park, said patrolling officers arrested the trio after they were spotted carrying 11 pieces of Siam Rosewood lumber.
The two men are local residents of the Buntharik district. They were identified as Samrit Sattrachai, 56, and Udom Tonphan, 46. The Lao woman was identified as Nu Kamchorn, 30.
Park officials said the three confessed to felling the trees to sell to a Chinese vendor on the Lao side who was offering Bt120 per kilo for the wood.