Reviewed by ThaiLawOnline, a licensed Thai law firm practising in Thailand since 2006. Thai lawyer of record: Wichuda Atthamethakon, LL.M., Thai Bar Licence 3149/2556.
Last updated on September 5, 2026
Legitimation (การรับรองบุตร, rap rong but, also called legitimization or acknowledgement of paternity) is the act by which a child born to unmarried parents becomes the legitimate child of the father. Under Section 1546 of the Civil and Commercial Code a child born out of wedlock is the legitimate child of the mother alone, whatever the birth certificate says. Section 1547 gives the father three ways to change that: marrying the mother, registering at the district office, or obtaining a court judgment. Until then he has no parental power and no standing in court.
Table of Contents
The three routes under Section 1547
Subsequent marriage. If the parents register their marriage after the birth, the child becomes legitimate automatically.
Registration at the amphur. The father applies at the district office, and under Section 1548 both the mother and the child must consent. If either does not answer, the registrar notifies them, and silence for 60 days (180 days if they are outside Thailand) counts as refusal. Registration makes the man the legal father but not the holder of parental power: under Section 1549 the mother or child may object within 90 days that he is unfit to exercise it, and the court then decides.
Court judgment. Where the mother refuses, has died, or the child is too young to consent, the father sues in the Juvenile and Family Court. Section 1555 lists the grounds, including a written acknowledgement by the father, his name on the birth register with his knowledge, open cohabitation with the mother at conception, or common repute as father. The court usually orders DNA testing and a social worker’s report, and can decide parental power and maintenance in the same judgment.
Practical points for a foreign father
The common misunderstanding is that a Thai birth certificate naming the father makes him the legal father. It does not; it is evidence of a fact, and under Section 1546 the mother remains the sole holder of parental power. A foreign father who has lived with the mother for years still cannot object if she takes the child abroad or blocks contact.
At the amphur the father brings his passport, the child’s birth certificate, the mother’s identity card and house registration, and certified Thai translations of foreign documents; the mother and child attend to consent. The court route commonly takes six months to a year. Under Section 1557 the effect is retroactive to birth, which cuts both ways: the father gains inheritance rights and standing, and his duty to pay maintenance under Section 1564 also runs from birth, so a court can order back payments.
What legitimation does and does not give
Legitimation creates the legal relationship of father and child: mutual inheritance rights, the maintenance duty, the child’s right to the father’s surname, and standing to ask the court for custody or contact. It does not transfer parental power, which stays with the mother unless a registered agreement or the court provides otherwise, and it does not let the father take the child abroad without her consent.
Time limits matter. Under Section 1556 a child under 15 sues through a legal representative, a child of 15 to 19 may sue alone, and a child who has reached 20 must sue within one year. A registration made without proper consent can be challenged under Section 1554 within three months of learning of it and at most ten years after registration.
Frequently asked questions
Can a foreign father legitimate a child in Thailand?
Yes. Section 1547 applies to any father, and the Act on Conflict of Laws points to the father’s national law only for his capacity to acknowledge the child. A foreigner registers at the amphur with the mother’s and child’s consent, bringing a passport and certified Thai translations, or petitions the Juvenile and Family Court where consent is refused.
Does legitimation give the father custody in Thailand?
Not by itself. Registration makes him the legal father, but parental power stays with the mother unless the parents agree otherwise in a registered agreement or the court orders it. Under Section 1549 the mother or child can object within 90 days that the father is unfit to exercise parental power, and the court then decides.
What if the mother refuses to consent to legitimation?
The father files an action in the Juvenile and Family Court under Section 1555. The court orders a DNA test and a social worker’s report, and if paternity is proven it declares the child legitimate, with effect from birth under Section 1557. The same judgment can settle parental power, contact and maintenance.
See also: parental rights, child custody, full (sole) custody, travel consent letter, and the full guides to legitimation of a father’s rights in Thailand and child custody in Thailand.
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