In reply to Pok:
Koh Yao has loads of climbing, and it's all pretty amazing. I'd rate it as much, much more than just a break from Tonsai - definitely worthy of a week or two trip in its own right. The Mitt alone has a few days worth of routes across the grade spectrum. Add the Grateful Wall for a day or two, plus some of the other crags, DWS and some time exploring an amazing island and you've easily got a couple of weeks. If I was out there these days I'd spend more time on Koh Yao and Koh Laoliang, but that's a matter of personal preference as I'm not too big on the noise/crowds and party scene of Railay/Tonsai. I'd do day trips across to the peninsula to do some big multi-pitch stuff occasionally, but not much more than that.
A perfect trip for me would be a few days in Tonsai/Railay, then a boat to Ao Nang - pick up a moped and ride out to Spirit Mountain for a day or two. When you're tired of that ride up to Ao Thalane and go across to Koh Yao for a week or more. When you're sick of that head back to Ao Nang, drop off the bike and head down to Laoliang for a few days, before heading home.
For me, a climbing trip is also a way of experiencing the local culture. It's easy to think you're getting that in Railay or Tonsai, but in my opinion you'll experience much more of Thailand and its amazing people/culture by visiting other areas these days. Some people don't want that, however, so each to his or her own. I'd assume that if someone travels all the way to Thailand to climb, then they're also interested in either the local culture (which is all but non-existent these days in Railay or Tonsai) or getting smashed every night (readily available in Tonsai and Railay).
Post edited at 12:19