Upvote:0
I would personally suggest giving yourself about 8-9 hours, maybe more.
This is what I did in the summer when I had a change at Changi.
The reason I suggest this is 1 you can relax and take your time and 2 this gives you plenty of time to go and be a tourist in Singapore :)
It's very easy to get from the airport to the centre on the metro system they have.
Upvote:1
Providing our inbound flight is on time then with no checked baggage, 1.25 hours is more than enough time. You will need to change Terminal from T1 to T2, but Changi has an efficient and frequent air train.
Also note that Changi has individual security per gate, so as long as you can reach the security queue before the gate closes, you should be ok.
The only pre-requisite will be that you are able to obtain a valid boarding pass for your Cebu Pacific flight. The Singaporeans are particularly picky when it comes to self check-in and often require self-printed boarding passes to be stamped by airline staff before they are valid for travel. I would recommend contacting the airline for advice.
With checked baggage, you would really be cutting it fine and would need all the stars to align (on time inbound, speedy immigration clearance, swift delivery of baggage, seamless transfer to T2, no check-in queues) in order to be safely checked in 45 minutes before your departing flight.