No personal experience with LASIK in Thailand (had it done in the USA), but Bumrungrad does have four or five ophthalmologists who specialize in LASIK, and at least two of them are board-certified in the USA.
If you call or send an email inquiry, they are usually really great about providing a ballpark price for a procedure. Generally speaking, the most significant billing variable at Bumrungrad is the physician fee (for normal, uncomplicated, routine procedures), so you might want to ask for estimates based on utilizing more than one doctor.
Be sure to tell them you're a medical tourist so they can advise you of any potential flight restrictions relative specifically to refractive surgery (e.g., must wait X number of days before flying after undergoing such-and-such a procedure).
Good luck!