via　https://www.ecitizen.gov.sg/Driving-in-Singapore-How-to-convert-a-foreign-driving-licence.html

If you are a Singapore citizen or PR

If you are a Singapore citizen or permanent resident (PR), you can drive in Singapore only after you obtain a Singapore driving licence. You must convert your foreign driving licence to Singapore driving licence as soon as possible if you want to drive in Singapore.　

New Singapore citizens and PRs must convert their foreign driving licences within 3 months of obtaining citizenship or PR status.