Not quite the same thing, but the desktop version of the Fediverse Observer site (which you can also see on mobile, if you ask your browser for the desktop version of the page) lets you filter by language and by country.
It does explicitly say in the description say that it is hosted in Vietnam, and people are clearly talking about Vietnamese stuff (in English), but is low traffic and has only two communities (with tens of subscribers).
There are no kbin servers presently registered as using Vietnamese language or as being in Vietnam.