Unlike in the US, where every arriving passenger has to go through immigration, you don’t have to do that in Singapore. I would assume there is a Scoot transfer/transit counter in T2 where you can get your boarding pass for your Hong Kong flight. The Singapore airport is the most efficient airports I have flown through. All the terminals are connected airside, and you can move within the terminals easily, if necessary. And even if you have to go through immigration and have to go check in to a different flight, things work smoothly.

I am assuming that this is two separate tickets/PNRs. The only concern that I would have is that there is a possibility that the US flight might be delayed and you might miss your Scoot flight, they probably won’t accommodate you on a later flight.