I've had master student who went on to pursue PhD or do postdoc in US/UK etc. and come back start assist.prof career. It is in fact not that difficult since local Universities also want to have more Singaporean-born professors to balance the team (lots of Chinese/Indian professor hired in last two decades so the ratio of local was kinda of a problem)
I'd say study hard and aim for a top PhD program in US/UK early on is a good strategy. You can focus more on theoretical research and publications if doing academia is your ultimate goal.
Pay-wise I know fresh PhD from US top schools join
NUS and get 120k/year. My professor who has been with
NUS ECE for 25 years when I was in school draws about 250k/year and prabably more now. It also depends on faculty. CS professor maybe similar to engineering. Business and law tends to make more especially if got consultation side-job. Medicine and dental professors are usually also practicing in
NUS as well and their pay is way higher.
But being a professor the first 5-10 years is not easy. Getting funding and generating publication to earn tenure is no easy task for young graduates.