The Thai Civil and Commercial Code provides the following:
Section 1548. The father could apply for registration of legitimation of the child only when the father has got the consent of the child and the mother.
In case where the child and the mother do not appear before the Registrar for giving the consent, the Registrar shall notify the child and the mother about the application made by the father. If the child or the mother has no objection or does not give the consent within sixty days after receiving of the said notification, it is assumed that the child or the mother does not give the consent. The period of time shall be extended to one hundred and eighty days in case where the child or the mother has been outside of Thailand.
In case where the child or the mother has an objection that the applicant is not the father, or does not give the consent, or is unable to give the consent, the said legitimation must be enforced by a judgment of the Court.
After the Court had pronounced a judgment that the father could register the legitimation of the child, the father then could take the said Court Judgement for the Registrar to register the legitimation.
Supreme Court Adjudication No. 13745/2553
According to the application of Section 1548, an application for legitimation of the child made by the father could not be effected if the consent of the mother and the child had not been received. The Plaintiff and the Defendant had cohabited as husband and wife with no marriage registration and the child was over 7 years old. Upon separation of the Plaintiff and the Defendant, the Plaintiff applied for legitimation of the child at the Dusit District Office. There was no consent given by the Defendant by virtue of the fact that the child was too young and the mother did not consent to the application. Even though the application to the District Office could not be effected, the Plaintiff was entitled to apply to the court for a decision effecting registration.
The Supreme Court held that the child was the legitimate child of the Plaintiff.