I strongly second Ko Lanta (presume that's what last poster meant by "Lunta"? Maybe American spelling varies). Plenty of options where to stay, but a quiet, relaxed atmosphere.

Pimalai is the swankest resort on Lanta. We stayed at Sri Lanta and loved it. You have many options from family-run cheap bungalows to nice joints like Pimalai.

Here's a tourism site for the island:

http://ko-lanta.com/home.htm