Regardless of how long the repair is going to take, you're required to renew your road tax once it's expired. You do have the option to lay up your vehicle if you will not be using it for an extended period of time. You can find more information here. Do note once you layup your vehicle.. the PARF rebate is forfeited.

https://onemotoring.lta.gov.sg/content/onemotoring/home/owning/vehicle-lay-up.html