In Surat Thani province, there is a lake. Choew Lan lake is artificial, a damn was built in 1982, to supply water and electricity. The lake is inside a national park, and on the water, float raft houses.
The raft houses are out in the far reaches of the lake, and accessible only by boat. You book a raft house, catch the boat from the municipal pier next to the dam and from there you can see caves, treks and take boat tours.
It's a life experience.
We had an ex travel agent with us to find and book a cheap price from one of the three National Park owned rafts. But there are several scattered all around the lake. The most famous, 500 Rai Raft Houses, wanted $250 a person, which was simply too much. We opted for a cheaper one, Sai Chol Raft, it was basic, but more affordable, and for around 2000 baht per person we had 3 meals, and a raft hut for the night.
The boat trip is extra, that is another 2000 baht per boat, but that did include trips around the lake, and a visit to a coral cave and bamboo raft trip. The coral cave is well worth seeing, but it involves a short, 1km, trek over a hill and the raft trip to get to it.
The food was plentiful, and is Thai style. There is limited western food available on this raft. It's amazing to be able to get up, open the door and jump into the lake first thing in the morning.
This lake is in Surat Thani which is roughly half way between Phuket and Bangkok. There is parking available at the pier. To book it, I'd recommend booking it via a travel agent. You will pay extra but it ensures you get a connecting boat and the sightseeing trips all arranged.
The nearest airport is Surat Thani, and its an hours drive from there to the pier. There's plenty of parking there, next to the pier, for 80 baht a night.