Hi Elvin, thanks for your message. Before modifying the exhaust system, you need to get LTA’s approval by submitting these for evaluation:

Certification from the product manufacturer stating that the proposed aftermarket exhaust system is suitable for the make and model of the vehicle.

Test reports from LTA- or NEA-recognised test laboratories to show that the aftermarket exhaust system, when fitted to your vehicle, complies with noise and exhaust emission standards for your vehicle model.

More details: https://www.onemotoring.com.sg/content/onemotoring/home/owning/modification.html