Agree that Amanpuri and Amanoi would be the best.

If you do not mind crowds at the beach during the day, I can recommend Rayavadee, Krabi. Cheaper than the Amans, nice (a bit dark, but still) bungalows and one of the most beautiful beaches in the world, but - as said - the longtail boats ++ will arrive there with lots of other tourists during the day. They cannot enter the Rayavadee private area (where the loungers are and where the service you require is), but will be at the beaches right in front of you.