I spent 3 years in Singapore and did most of my riding with ANZA. The club has several hundred members and there's around 5-6 different rides of varying distance/pace heading out on the Saturday morning. http://www.anzacycling.com/anzacycling/Home.html
There is another large club called Joyriders.
The rides do tend to start early, 5:30 wheels rolling, (there is a later 7am ride on a saturday).
I also used to commute to work every day solo (40km round trip). To be honest, some of the drivers don't think bikes should be allowed on the road, and a lot don't know how to drive considerately around cyclists, but I never felt threatened or that someone was out to get me. I find London a lot worse.
The terrain is mostly flat although there's some rolling terrain and a few little sharp little rises to be found. The biggest "hill" is Mt Faber, which is about a 5 minute climb.