Originally Posted by percysmith

"If you’re departing from Terminal 4 but want to access different terminals (which is the only problematic scenario, since Terminal 4 isn’t easily connected to the other terminals), either:

• Go to the early check-in desk in the Jewel and make sure you get a printed boarding pass with a stamp on it, and then you can clear security at T1-T3
• Go to T4 and clear security there, and then take the airside bus, which will allow you to access other terminals"

https://onemileatatime.com/singapore...-access-rules/