I stayed at all of the following properties and would recommend all of them in the order given (they should all be within your budget):

- Le Meridien Khao Lak
- The Westin Langkawi
- The Westin Nusa Dua
- The Laguna Bali
- Sheraton Krabi
- The Westin Siray Bay
- Le Méridien Angkor (at the bottom of the list because it's not on a beach )
- Plaza Athenee Bangkok (at the bottom of the list because it's not on a beach )

The St. Regis Bali is close to the other Bali properties I stayed at so I could get a glimpse at that as well. It just looks stunning, though it might not be within your budget...