Can a foreigner buy a stilt house above the water in Thailand?

You cannot actually own these houses as a real estate property as it has no official ownership title deed. These houses on stilts only exist with the allowance of the marine department. You as a foreigner cannot claim any rights in such area. A tabien baan is a house registration book, it is merely an administrative document and registers residents who live there and it states their official domicile/ address. It is not in any way an ownership document and you cannot claim any damages when they would withdraw allowance for the locals to use this area.