Hi, the first thing you can do is to save any dash-cam footage. The next thing you can do is to take a photograph of the car license plate and the Malaysian Road Tax Disc.
If both parties agree, you may opt for a private settlement and have your own arrangements.
Alternatively, you can make a police report. The police report should be done immediately after the incident. The police would have the ability to prevent the car to leave the country should they deem necessary.
If these suggestions fail, you may wish to file a report Persatuan Insuran Am Malaysia (PIAM) and General Insurance Association of Singapore (GIA).
Hope this helps.