There are about a dozen budget options in Cherating (which is a very small town spread over 2 streets) and there isn't a huge amount of difference between them all. I looked at rooms at 8 of them, and decided I liked Mata Hari best.
They have about a dozen basic wooden cabins clustered around a central green area. All the cabins have large front porches. The cheapest ones are small A-frames and share the use of a toilet block (I think those ones were 20 or 25RM a night). The larger cabins have their own ensuites and a couple of windows, letting in a bit more light - I stayed in one of those for 40RM (about £8) a night.
Like all the budget options in town, the showers are cold water only, and the cabins are very rustic, but I found the bed comfortable, and it was reasonably clean. They made up the bed with fresh sheets when I arrived, and offered to change the sheets after a couple of nights. There was a comfy chair as well as a table on the porch, so I could sit out there and relax, and a mosquito net over the bed, in case I wanted to leave the windows open in the evening to catch the sea breeze.
There's a communal lounge area with a small kitchen, so you can prepare some basic food as well as tea and coffee. The owner and the staff were all pleasant and friendly.
Cherating is so small that everything is only a couple of minute's walk. There's a convenience store and a few cafes going one way along the main street (towards the main road, where the bus drops you off). Turn the opposite way and you'll find the best and cheapest place to eat in town, a strip of 3 restaurants with outdoor seating (some of whom are open for breakfast and lunch, others for dinner). A basic meal there will set you back 5-8RM. There's a fruit vendor truck that stops there very briefly in the mornings, and an internet cafe there as well (which I found to have the fastest and most reliable wifi in town). The bar on the beach is also a laid-back place to hang, and they serve excellent watermelon shakes.
I turned up intending to stay 2 nights, and ended up staying 4 or 5. Cherating is that sort of place. Stayed January 2011