With $3 billions bets worth he made nice money! Now he will be arrested and sentenced few months in jail or house arrest, he will pay some official fines, he will bribe judge and police, and in 2-3 months he will open a new casino! It's how it goes!
I don't know about the laws in Vietnam, but they have some restrictions probably. Illegal casino can offer games you can't find in legal casino, you can have higher bets (without limits), which can be good for some gamblers who just get in and get out, without need to register or report their winnings and pay taxes for that!
People will always find a way to bend some rules! In the end rules exist to be broken