I can only add that I stayed at the six senses in samui and was not happy at all. Serious privacy issues where your neighbor can see straight to your pool area or through your window. Also beach was a very long walk away down a lot of steps from a cliff,,, pool area was nice though but who wants to stay by the pool all day long!!
I went to see BT and it was very nice although a very large resort with over 200 villas and rooms.
There is another nice boutique property called Library that is also quite nice.