Most small Thai builders are 'fixers' and just oversee labourers and use sub contractors for skills. If you have the time to source different subcontractors to do all the different stages and buy the materials yourself you can cut out the "overseer" . Beware you will need to be on site daily and will need to check everything is being done to your requirements. Do not trust a contract or any paperwork drawn up in Thailand. All the paperwork in the world will not protect you from the builder walking away. Yes you can sue him - Many have tried and won but still have not got their money back ( I heard one story that the courts allow up to 10 years for repayment)!!
Most Thais will continue to fix and repair until you have paid them but not all. Some will walk even without getting paid if they do not like what they are doing.
In my experience do not pay in front ( small advance to cover materials OK)
If you do not speak Thai get a translator to ensure your needs are understood.
The need for complicated and expensive plans is far outweighed by the builders experience and ability. Most Thais will always say yes and agree with you even if they do not understand what you are asking. This is I think do to the loss of face admitting that you know more than them.
Again in my experience this will be avoided by letting the builder tell you/show you what he is capable of rather then you presuming and then being dissapointed.
This advise only applies to using a local builder directly as I have done.
I also tried using a university qualified architect - Great for paper houses!!
Keep It simple and do not pay in front and you cannot go wrong - you will go insane but you will save money and get what you want - eventually
