This is going to be tight. You're having to go from a domestic Thailand flight connecting to an international flight. Keep in mind that BKK airport (sorry can't spell the proper name) is huge - it took me nearly 30 minutes to walk from one finger to another, and this was on the airside, although to be fair I was going diagonally across. The good news is that I assume that Bangkok Airways should land pretty much on time. Whether or not you can make it to the Air Asia check in with your checked baggage is a different story (don't forget, you'll have to clear passport control after that).