Hey, if you have the money to splash, why not try Natula...i bet many travellers do not know of this heavenly island..You can take a flight from Denpasar (Bali) to this island...clear blue waters, truly a Shangri-la! Maybe the visit will be etched in your memory forever! Conoco, the oil company has a stake here.
would deffo recommend Koh Samet and Koh Chang in Thailand. Not too many people head down that way. The beaches are really nice and quiet and there are some really nice (cheap) places to stay. If you go to Koh Chang make sure you check out some of the surrounding islands.
In Malaysia, the Perhentian Islands are absolutley stunning, we thought they were far far better than any of the islands in Thailand (don't get me wrong, we loved Thailand's little islands but the Perhentians blew us away)! really peaceful place with great diving/snorkelling and beautiful beaches.
Easy pick for me! I loved Koh Kood in Thailand, which is a part of the Koh Chang archipelago in the eastern Gulf of Thailand. If it's peace and quiet you want with no crowds and practically no development, that's it! Keep in mind, though, the less development you have, the more limited your choices will be, especially regarding food. I'm a picky eater, but I have to say I finished just about everything I ate while I was there. I stayed at the Aow-Noi Resort, which has its own beach. I'd be glad to e-mail you specifics if you like!