Airside transit or entry?
A transit traveller continues to another country without clearing Singapore arrival immigration. Collecting baggage or tickets and checking in again may require entry, so check the airline’s arrangements. A self-transfer requiring immigration clearance must meet ordinary entry requirements.
Check the onward journey
Ask the airline whether bags/tickets can be transferred airside or require entry and re-check-in. Meet the destination’s own entry requirements. A flight connection requiring Singapore immigration clearance must satisfy Singapore entry/visa/SGAC rules as applicable.
Official ICA source
Written independently from ICA’s English original. The linked source supplies the complete document and subsequent updates.