This was quite a dated post, as it occurred about 3 weeks back. I learnt about how the nasty Simlax setosa can be: vigorous growth that smother and cover over trees and almost impossible to eradicate since they can regenerate themselves as separate individuals from their stem cuttings.
This is my first time seeing them flower. In fact, all these while, I thought that they propagate vegetatively. Apparently I was wrong!
Because of its abundance, the mass flowering of it at Kent Ridge Road make it quite spectacular! Like little pom-poms, they look a little like Hoya or Uncaria as commented by A and WF.