The crags are near Krabi. Get to Bangkok, then Phuket, and then a three hour drive to either Krabi or Ao Nang . Then take a long tail boat to Railay Beach, which is only accessible by boat. It is approx. 15 minutes by boat from Ao Nang or 50 minutes from Krabi .
Boat travel is cheap and fun.
The place is a rock climbers Nirvana. King Climbers and the 6 or so other climbing schools run courses of all standards and if you are on your own they will climb and guide you for a very reasonable charge. The guide can also be bought in Rai Lay where it costs 450 baht. Some of your money will help go towards re-equipping. The local climbers are very nice people.