Probably Fujianese organized crime. The Triads from Hong Kong and Taiwan are not really connected to these large scale prostitution networks, but the Fujianese Gang (or Fuk Ching or any other name they're going by) run massive prostitution operations in multiple countries. These operations started in New York, but they also are detected in Western European countries like Italy, Spain, France, Belgium (especially in Brussels), etc...
As far as I know, in the United States, certainly here on the eastern seaboard and especially in the NY-Tristate area, these sprawling prostitution rings (networks really) are headed and operated by Chinese and Korean racketeers.
Maybe on the west coast in California and nearby states some Japanese Yakuza are involved too (no doubt,) but the Chinese and Korean have become very prominent in this racket.
