Based on the poor-quality of the photos (and my limited knowledge of Singapore insects) it would be very difficult to definitively ID this to species.
However, based on the shape and size, you're very likely looking at a species of ladybird beetle (aka ladybug; family Coccinellidae).
Specifically, I think this is a member of the subfamily Chilocorinae.
That looks like a Tropical leatherleaf slug.
The Tropical Leatherleaf (Laevicaulis alte) is found in both urban and forested areas. The animal is brownish, usually with darker speckles, and has a pale line on its back. It is not known whether it is native or not, though scientists think it is most likely introduced. It can grow to about 4cm long.