Looking at an itinerary with Cebu Air via MNL arriving from SIN @ 0540 and departing for HKG @0715, have 1h 35m between flights, only carry on.

Is 1h 35m enough? Is there an international transfer process set up at T3 (Cebu Air terminal), so that I do not have to go through immigration/arrivals? What will the transfer process be like?

Unfortunately Cebu Air do not want to sell this itinerary as one ticket, as they require minimum of 4h connection time. So will book as two separate tickets. At SIN, will they be able to check me in and give me the boarding pass for the MNL-HKG flight? If not, are there transfer desks at MNL, or will I have to clear immigration and go normal route via departures?