We use Bangkok Airways between BKK and UXM (? Koh Samui, anyway) and are thrilled with the performance of this little-but-growing airline. I'm pretty sure they serve Phuket now, too. Most of UXM is on ATR-72's, with the occasional 717. Fares are dirt cheap - usd 100 RT, more or less. They have a web site where you can book. No FF miles afaik, but they make up for it with a snack service that's respectable, and overall really, really nice service - almost a tiny regional Cathay with toy airplanes.