For cheapest and not too isolated I recommend one of the resorty areas in Thailand or Vietnam. (VN will be cheaper.)

Phuket for example in Thailand, you have your choice or resorts, some excursions and a town center to play and eat.

Hoi An in Vietnam is nice, not nearly as developed as Phuket, but there's a nice quiet beach with some hotels and there's also a touristy town center with delicious food. When I last went a couple of years ago, they were also building up the resorts in Danang, but those are more self-exclosed. The Hyatt is one of them I saw them building, there's other like the Crowne Plaza too.
http://danang.regency.hyatt.com/hyat...index.jsp?null