House build Hmmmmmm.

1) Keep the design as simple as possible, open plan, living/ dining room and adjoining kitchen. Easy design as possible and for the Thai builders to follow.
2) Allow about 12-15,000 Baht per square metre which should cover labour, materials (wall and floor tiles) and a decent kitchen with a couple of impressive extras.
3) Ceilings should be at least 2.8 metres in height and make sure you ask your builder to stick pesticide irrigation pipes within and under your base floor slab before he pours it. The termites and borers here are murder.
4) Make sure you employ a good electrician and become personally involved in the daily checking of dimensions and wall alignments (at least at the start).

Oh, and most importantly and when you sign a builders contract make sure you get copies of the builders I.D card, his house title book, preferably some reference documents and a contract written in both English and Thai. Have a locally trusted and endorsed solicitor go through it with you and before you sign up.

Many, many more suggestions and help that the other good folk here will happily provide if you ask nicely .

Good luck dantomat and welcome!