i've always taken a bus from mae sai to chiang rai or chiang mai on border runs. but i was wondering if there was one to thaton or fang on the western side. i dont recall seeing anything listed at the mae sai bus station. but thought i'd ask here

there are red pickup buses that will take you to the bus station and you can get a bus from there or just walk along the lines of red trucks in Mae Sai and ask who goes to ThaTon. Then get a bus from TaTon to Fang .