Here's the full info from the
Changi website:
Left Baggage
You can have your luggage looked after, if you need to leave the Airport. This service is available 24 hours.
For enquires, please email :
[email protected]
You can contact the personnel at the 24-hour service counter at Tel : (65) 6214 0628 (Terminal 1, Basement West #B21-62) and Tel : (65) 6214 1683 (Terminal 2, Arrival Meeting Hall North #016-024).
This service is also available 24 hours daily inside both the Departure/Transit Lounge in Terminal 1 (Departure/Transit Lounge East #021-19 Tel : (65) 6214 0318) and in Terminal 2 (Departure/Transit Lounge South #026-068Tel : (65) 6214 0448).