In Phuket, I find it better to be in a secluded location.

Trisara and Amanpuri are fantastic, even the entry level accommodation.

You might also consider:

The Boathouse (Same owners as Trisara, and very promising)
The Chedi
The Royal Phuket Yacht Club
Anantara
The Naka Island (formerly Six Senses, now Starwood Luxury Collection)