tafy...as a resident of Hat Yai, and a farang, as well, I have also looked for a Thai teachers. Several of us have attempted to find a school or teacher willing to take us under their wing...no dice. You can arrange for a 'teacher' at about 600 baht an hour (welcome to 'farang have money, I charge much'). It's more than you would pay for English lessons from a native speaker.
Find a good student, arrange some kind of reciprocal agreement - Thai lessons for English lessons.