The two by-far most-discussed and best-liked properties on this board are Amanpuri and Trisara.

I went to both earlier this year on honeymoon, and enjoyed them both greatly, though they had different strenghts and weaknesses - I posted a lengthy trip report. Musken also posted an excellent trip report comparing the two properties.

We spent most of our time in the resorts in Phuket, and loved it as a beach destination with great views and weather. There are also great boat trips to be had. However, if you're interested in the cultural side of things, rather than R&R, there are definitely destinations that offer more on that front (even within Thailand).