If you are visiting SG in between HK and Thailand, your experience is likely to be better in those other places, LOL!
But SG can be quite fun as well, and your non-punting plans are solid, hawker center foods are delicious!
If you like variety and an opportunity to window shop, I would not tie myself down to one indy escort found on facebook. If she ends up being a bust, then that practically ruins your entire trip. I would keep my options open, and one place to visit is BRIX, which is a popular bar / pickup joint in the Orchard area, I believe it is located at the Hyatt. LOTS of options here, and everyone is available, for a price. This way, you get to pick!
I've had good success with SA (seekingarrangement) in Singapore, but that would require some research and planning ahead of time. I have found some really nice amateurs, girls working in regular paying jobs who would enjoy hanging out and having sex with successful, affluent, and more experienced men for a small/medium/large allowance.