4hr stopover Changi…feasible to get to Jewel?

[carreauchompeur]

Hi folks, flying into SIN from Thailand on Jetstar, have 4 clear hours before departure on Qantas to London.

I only ask as it was an unexpected faff getting from T4 to T1 on the incoming…

…is this a feasible length of time to get through immigration, to the Jewel for a wander and then back through T1?

Luggage is checked through from Thailand.