The US claims the four are members of "the Zhao Wei translational criminal organisation" (TCO).

"Based in Laos within the Golden Triangle Special Economic Zone (GTSEZ), the Zhao Wei TCO exploits this region by engaging in drug trafficking, human trafficking, money laundering, bribery, and wildlife trafficking," the US announcement alleged.

 Since 2014, Thai, Lao, and Chinese authorities have seized large narcotics shipments that have been traced to the Kings Romans Casino."

https://www.bangkokpost.com/news/crime/1404590/us-sanctions-laos-based-criminal-organisation