I have friends currently hiking and travelling in the border area between Thailand and Burma/Myanmar. These are seasoned, experienced travellers in Thailand, Bali, India, Nepal and so on.
They raved about Mae Hong Son. Check out the night market there...beyond that, I'll quote their email to me:
Mae Hong Son is an absolute gem of a town. A small lake in the centre is ringed by noodle shops and Temples. Every night the local hilltribe people make the trek from the mountains to sell their wares on the street. The Wats (Buddhist temples) spread throughout the town and surrounding hills complete the fairyland setting. This town sits in the middle of what is known as the Mae Hong Son Loop. Burly Australian bikers rent motorcycles in Chiang Mai and do the 800km stretch along the Myanmar border returning to Chiang Mai from the south.