Hi Andrew, you can go by boat from Krabi or Ao Nang to Rai Lay, and put up a notice on the message board near King Climbers shop (Near Ya Ya bungalows). I had no trouble finding someone to climb with this way. Alternately, just head to the crags and start chatting to people. You can also hire guides from the 4 (or more)climbing schools, who supply gear and take you to various spots. I watched them leading barefoot up grades 18 and 19 to set up topropes for their customers. King himself may be able to offer you more info. I emailed him at [email protected]. This address is an old one, as I was in thailand 4 years ago so may not be accurate.
Good luck, the climbing is fantastic, but beware of loose bolts on upper pitches.