I am not very sure, I will go with Stocky on that: "they do have a culture of filial respect and responsibility that can become an onerous burden". And it falls on the daughter(s) shoulders in Thailand, not the son(s), and the burden is not only about helping the parents but the brothers also.
We got some girls in our company who went into huge debt just to help their w####r of a brother, or father, and we're talking middle class here, so not specific to poor Thai people.
So I would also indeed advise some caution when getting married in Thailand, knowing the family is as important, if not more, than knowing the girl you're going to marry.