There are many illegal casino in China.
I mean most Chinese people play mahjong, cards and bet a lot of money.
But there are also places where you can bet money playing with machines.
You don't bet actual money!
Instead you exchange your money for some token. You can win more token and then exchange these token back for some money! I believe this is a way to hide and pretend the place is some gamers club.
Anyway these illegal casino are known by the local police and a way to make some extra cash at the end of the month.