This is indeed a true bug (Hemipteran) in the infraorder Pentatomomorpha.
As Arthur Frost said in his comment, exact identification is difficult for those of us on the other side of the world.
However, a fortuitous series of internet rabbit holes may have led me to a very similar looking specimen.
Homoeocerus striicornis and Homoeocerus angulatus appear to be quite similar in appearance to your insect, and so I would not be surprised if your insect was at least in this genus (see here for more pictures) within the "leaf-footed bugs" family (Coreidae).
- I'd say Homoeocerus angulatus is more likely only because the sightings maps on inaturalist show this species being found in Singapore.
I can't say that any incredibly reputable or peer-reviewed resources in English online provide definitive support for this identification, but this is at least a step in the right (a?) direction.