Unmarried foreigners, or foreigners not married to Taiwanese?
If the former, many of narrowly defined expat may be excluded.
The definition of expat is not clear. Some people dnt think English teachers or students are expat.
According to Wikipedia, blue collar workers could be included. I understood they are not subject to your question, though.
An expatriate (often shortened to expat) is a person temporarily or permanently residing in a country other than that of their citizenship.
In common usage, the term often refers to professionals or skilled workers sent abroad by their employers, who can be companies, governments, or non-governmental organisations. Effectively migrant workers, they usually earn more than they would at home, and more than local employees.
However, the term ‘expatriate’ is also used for retirees and others who have chosen to live outside their native country. Historically, it has also referred to exiles.