If you have a little time and some inclination you can have some real adveture experiences in Khaoh Kong. Not much is organised yet, but you could start by dropping in and talking with Nick at Sauna Garden, opposite the Thai restaurant. Ask around for him. He organises motorbike trips into the mountains and has some info about treking. There was some talk about kayak trips too.
Must visit bars include the sunset bar on the river and Cat bar , also on the river opposite the speed boat dock. Like something from a seedy Graham Greene novel. This is old school Asia, before the invasion of the flashpackers and Insipid.... sorry, Intrepid folks.