Do Singaporean immigrants need to go to an immigration prison?

There are no immigration supervisors in Singapore. If you only get a Singapore green card, but your passport is still in China and you can't stay in the United States for a long time, you still need a visa to enter the United States. If you are a Singapore citizen and hold a Singapore passport, you don't need a visa to enter the United States. It is ok to stay for a long time, but some simple procedures are still needed.