Thais vary, just as they do elsewhere in the world. Some are trustworthy (I have even met some nice, honest policemen here), some should be part of someone else's life, not mine. I the wife signed the usufruct without batting an eye, a good sign. While prenups may be legal, I doubt whether a Thai family would have heard of it and would surely be suspicious (as in, are you trying to cheat my daughter?).