How did Peter Hoang escape from Vietnam to the United States?

By being a refugee

Explanation:

Peter Hoang was a Vietnamese who who was heavily into gambling. He went to Casinos regularly to fulfil the desire. He escaped from Vietnam to the United States by applying for asylum as a refugee which was later granted.

He was also a drug trafficker and was shot to death in a Sydney suburb and the identity of his killers remains a mystery up until now.