I can help a bit on that one. Yes, the westerner left all to charity. I know why. Old people see things on TV and believe they can help and don't think about responsibilities or they no longer wish to keep things the same or a momentary lapse.
The Thai guy was surprised as he had been told different for many years. When you are told and you believe, you don't continue to inquire.
Plus, in every relationship, there is one who has more and in this case, there was one who had nothing. Not an equal dynamic.
True, this is a life lesson for the Thai guy. But, one that he will unfortunately deal with for the rest of his life.