Whether you need to clear immigration at Singapore Changi Airport depends entirely on how your flights are booked. If you are on a single itinerary (one booking number) with Singapore Airlines or its partners, your bags are checked through to your final destination, and you can stay in the "Transit Area" without clearing customs or immigration. However, if you have booked separate tickets on different airlines (a "self-transfer"), you must clear immigration, collect your luggage from the arrival hall, and then re-check it at the departure counters in the public area. This requires you to have a valid visa for Singapore if your nationality requires one. For those in transit for more than 5.5 hours on a single ticket, Singapore offers free city tours, which do require you to clear immigration briefly. For travelers from countries like India or China, the 96-hour Visa Free Transit Facility (VFTF) may be available if you meet specific criteria, allowing you to enter the city during a long layover.