Wondering if anyone has been to Koh Kradan (Trang Province) recently? We were there pre-Tsunami, so I can't speak to how things are now (re-built, unscathed, etc).
Saw posts for other places farther up the coast and a lot of complaints about too many people and too expensive. Obviously it's been a number of years, but when we were there (two separate times), the place was beautiful and all but uninhabited.
If you're looking for niteclubs and bars, don't go, there aren't any. If you're looking for beaches all to yourself and great snorkling and don't mind poor water pressure in the showers and intermittent electricity, look it up.
A step up (at least 6 or 7 years ago) was the resort on Koh Ngai. Similar island to Kradan. Clean, isolated beaches, surrounded by reef.
Both are a easy long-tail boat ride from Koh Mook (Muk?) and Tham Morakot (the Emerald Cave). It's really a pitch black cave, but that opens up into a small beach completely enclosed in 40 or 50 ft (10-15 m) sheer rock walls.