A couple of places I can think of, not too luxurious though.
Excellent service at both locations
Tioman Island - Japamala Resort
(small private beach, kind of rocky)
Nikoi Island
(Off Bintan Island, Indonesia, approx 3 hours via ferry/car)
Couple of other destinations over @ my
travel blog with plenty of pictures, but seeing you'll like a good beach, Nikoi Island is my top choice ^