ICA这样说
http://www.ica.gov.sg/page.aspx?pageid=132#overseasbirth
An overseas-born minor (child) may be eligible for Singapore Citizenship by Descent under Article 122(1) of the Constitution of the Republic of Singapore, if his/her parents meet any of the following conditions:
The application has to be submitted within one year of the child's birth. Otherwise, a letter of explanation and additional documents are required for the late submission.