How do I apply Singapore citizenship for my child who is born overseas?

If one of your child's parents is a Singapore citizen, a Singapore citizenship application can be made online via ICA e-Service by the Singapore citizen parent using his/her Singpass account. In order to submit the application, the child is required to already hold a foreign birth certificate issued by the authority in his/her country of birth. You are encouraged to submit the application before your child turns one-year-old to facilitate the processing of your child's application.

This information provided here is sourced from the ICA website.