If you want to spend the night at the airport, I can tell you for sure that it is absolutely impossible. The airport will be closed after all inbound and outbound flights, and before that, the security personnel of the airport will clear the entire waiting hall in order to prevent suspicious people or suspicious items from hiding in the terminal building. Except the airport staff, other irrelevant personnel, including passengers (flying the next day), are not allowed to stay inside. With luck, I just said that the premise of airport closure is "after all flights in and out of Hong Kong on that day have ended normally". If there is a big delay in the inbound and outbound flights (unless the flight is cancelled or sent to the hotel), you can stay in the waiting hall until the plane is normal.

If you want to spend the night around the airport, in my experience, there will be no good places around the airport, only hotels and guesthouses. Of course, there are many places that are open 24 hours a day, such as ktv, Internet cafes, bars, Taobao, coffee shops, hot pot restaurants, restaurants, McDonald's and KFC. It depends on whether you want to lie down or sit for the night.