We just got back from Thailand... low season is wonderful! No lines for routes and cheap bungalows. I don't know about Oct., but currently Tonsai only has electricity from 6pm-6am most places, so you must be okay with the heat. There are places to climb in the rain on Tonsai. And if it rains, just go deep water soloing! We also stayed on Phi Phi Don for a few days. Our hut was on a really nice beach and a three minute walk from our door to the base of a crag. Not a huge amount of routes, but a few nice ones. A great place for a chance to lay on the beach and just relax and also climb with nobody else around.
"The best climber in the world is the one who is having the most fun" - Alex Lowe