You can renew your passport in advance in Singapore. The Immigration & Checkpoints Authority (ICA) allows Singaporean citizens to apply for a passport renewal up to one year before the expiration date of their current passport.
This means that if your passport is still valid but will expire within the next year, you can submit an application for a renewal. Keep in mind that your new passport will be issued with a validity period of 10 years from the date of issuance, regardless of when you apply for the renewal.