Great thread Jonny. I am at the final stages of planning a very similar venture in a rice field outside Chiang Mai - everything slightly larger, but same same.
Did you consider earthquake 'proofing'? Chiang Mai is a 'moderate' earthquake risk area. There was a 6.8 quake in Burma that rattled the north in March 2011 and there have been many more big ones over the past 100 years. Current building regulations, if followed properly, should safeguard your house but only up to a 4.5. I'm currently discussing this with the builder and looking at ways to safeguard to 6.5. Glad to hear any tips.