You can trace it yourself, provided you can information from his
email. The email header usually reveals a lot, and if you know how,
you can trace it.
Anyway, most people in Singapore uses dynamic IP addresses,
meaning, even if you managed to trace, the most you can get out of
it is their ISP.
I'm not quite sure whether you can report police. Unless the person
causes damage to you, nobody bothers to make a police report.