You may already be aware of this, Koh Samui got badly pounded by heavy, heavy rains and high winds last weekend. Bangkok Airways cancelled their flights in/out for at least two days.

That said, you should head over to the Thai Visa forum where you should be able to find the information you seek. There is a Koh Samui sub-forum. At least a few members reside there year-round, and I do know there is ADSL there, although I am not sure about the coverage.