Well there is also a strong Cantonese community who were either traders originally, or brought over again to work on plantations post slave liberation. (Similar ethnic make up to Mauritius)... Not that that explains Bangkok, but I guess Bangkok is a good transit point.....

It's probably more of a simple out bound holiday destination..... Expat french metropolitan Reunionais (at least when I lived there) generally get a 40% surplus on their national salaries, yet rents, and local food can be bought cheaply. I often travelled to Australia (on Air Mauritius), South Africa, Kenya, etc for holidays. Theres a good million people living there, with a sizeable wealth base, although huge inequalities in wealth do exist.