I had a bungalow built 2 years ago 120 sq m, 2 bedrooms, lounge, kitchen and toilet come shower total cost then was 965000 baht. Friends of the girlfriends did the same thing (similar build) a year ago and the price was 1150000. I would say you are probably looking at anything between 1100000 and 1350000 depending on materials. One tip I would give you is do not let the builder know you are a foreigner as those prices will likely change and not for the better either.