Your application to extend your stay will be withdrawn if payment is not made within the time frame as indicated on the In-Principle Approval notice.  

If your application in withdrawn, you will need to submit a fresh application online via the e-Service. Otherwise, you are advised to depart on or before the expiry date of your existing short-term visit pass (STVP).   You are reminded to monitor your application status online and make the payment promptly within the specified time frame once you received the In-Principle Approval notice.

This information is sourced from ICA