All applications must be done online at the Singapore Immigration and Checkpoints Authority's website. The Singaporean parent may submit an application for a child who is born overseas and who meets any of the following conditions:

The father, who is a Singapore citizen by Birth and has a lawful marriage,
The father, who is a Singapore citizen by Registration and has a lawful marriage. The child shall not acquire citizenship of the country he was born by reason of his birth in that country.
The mother, who is a Singapore citizen by Birth and the child born on or after 15 May 2004.
The mother, who is a Singapore citizen by Registration and the child born on or after 15 May 2004. The child shall not acquire citizenship of the country he was born by reason of his birth in that country.
The father (who has a lawful marriage at time of child’s birth) or mother is a Singapore citizen by Descent has to complete an additional Annex form to the application declaring their residence period in Singapore. The application can only be accepted if the applicant fulfils the requirements stipulated in the Annex.
Note: The application has to be submitted within one year of the child’s birth. Otherwise, a letter of explanation is required for the delay in submission. In order to fulfil two of the Singapore citizenship application’s requirements as stated in ICA website, the child's parents must be legally married at the point of application and the child has to have an official Vietnam birth certificate which can be obtained at the City/ Province Justice Department.

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