Their food is mainly imported, their cars are imported, they do their shopping in HK, Paris, Milan and Monaco. Their bank accounts are offshore and in New York or London. And what will they do? There is no Channel fashion show, men's tailors are not up to Saville Row or Milan standards. All in all even if rich people buy a pad here, they will spend little that benefits the Thao economy.
Ralking of shopping, a rich friend used to offer well dressed Thai women a weekend of shopping in Hong Kong. It is a much more effective opening gambit than many. Very few turned him down, even married ones.