Am planning to visit Thailand in late Feb/early March. I have visions of that perfect little thatched-roof hut that stands on stilts in the water - and that you can jump out of right into the ocean - maybe 20 feet from the shore. Not sure if a place like this exists in Thailand - but if anyone knows, would appreciate if you could let me know. Not really on a budget.
Thanks.

Maybe not on the sea, but if you want to jump out of your bungalow/hut straight into water, try staying on the Ton Toey raft station on the HUGE lake inside Khao Sok National Park. It is fantastic.

Only place I've seen built over the sea ( as opposed to fresh water ) is the Muslim village near the "James Bond Island. Hardly the perfect little thatched-roof hut though.
There are a number of hotels next to rivers that have raft rooms.
Inle Lake is in Burma, and not a proper reply to your post.
Koh Lipe certainly has exactly what you are looking for.
My wife and I visit Phi Phi every year. From our bungalow we walk ten yards and are in the sea. Paradise!! Take a look at the photos on our website and see for yourself. Loads of info if you want it.
Leigh Travel Club