Legitimate Child in Thailand: Rights Backdated to Birth

ปรับปรุงล่าสุดเมื่อ 12 ตุลาคม 2569

A child born to parents who are not married is, under Thai law, the child of the mother alone. That one rule decides who inherits, who can claim maintenance, who signs for a passport and who has any say if the parents separate. Becoming a legitimate child in Thailand changes all of it, and a Supreme Court decision published this month confirms that the change reaches back to the day the child was born.

Decision 6436/2562, added to the Supreme Court database on 11 October 2026, allowed a father to keep an arbitration award of 800,000 baht for the loss of his daughter’s support, even though the marriage that legitimated her was registered a month หลังจาก she died in a road accident. This guide explains the three routes to legitimation, what Section 1557 backdates, and what being a legitimate child in Thailand means in practice for Thai-foreign families.

Legitimate Child in Thailand: What the Status Actually Means

Section 1546 of the Civil and Commercial Code states that a child born of a woman who is not married to a man is deemed the legitimate child of that woman. The father is simply absent from the legal picture, whatever the couple’s domestic reality.

The practical consequences are wider than most parents expect. Until the child becomes a legitimate child in Thailand, the mother holds sole parental power under Section 1566, the father cannot be ordered to pay maintenance under Section 1564, he is not an heir of his own child, and he has no standing to consent to a passport application or to resist the child being taken abroad.

One point surprises almost everyone: naming the father on the birth certificate does nothing. Nor does paying for everything, living together for fifteen years, or appearing in the house registration book. Only one of the three routes in Section 1547 creates the legal link. Our detailed walkthrough of that process sits at legalisation of a father’s rights in Thailand.

The Three Routes to Legitimation Under Section 1547

Section 1547 is short: a child born of parents who were not married to each other becomes legitimate by the subsequent marriage of the parents, by registration at the district office, or by a judgment of the court. Each route has a different cost, a different timeline and a different failure point.

เส้นทาง	วิธีการทำงาน	Main obstacle
Subsequent marriage (s.1547)	The parents register their marriage at any district office. Legitimation is automatic, with no separate application.	Requires both parents to be free to marry and willing to do so.
District office registration (s.1547, s.1548)	The father applies to register the child as legitimate at the amphur.	Needs the consent of both the child and the mother. Silence for 60 days counts as refusal, and the father must then go to court.
Court judgment (s.1548, s.1555)	The court declares the child legitimate, typically on DNA evidence plus proof of cohabitation at the probable time of conception.	Slowest and most expensive route, but the only one available where the mother or child objects or cannot be found.

Section 1555 lists the circumstances in which a paternity action may be brought, including cohabitation during the period of possible conception, documents acknowledging the child, and public reputation as the father. Where the mother is unmarried and cooperative, the marriage route is almost always faster and cheaper than litigation.

Supreme Court 6436/2562: A Marriage After the Death Still Counted

The facts are stark. A couple lived together as husband and wife without registering a marriage, and their daughter was accordingly illegitimate. On 3 April 2016 a car insured by the insurer in the case collided with a motorcycle on which the daughter was a passenger. She died at the scene, aged about twenty-one.

On 3 May 2016, one month after the accident, her parents registered their marriage. The parents then pursued the insurance claim through arbitration, and the arbitrator awarded the father 800,000 baht plus interest for loss of support. The insurer asked the Civil Court to set the award aside under Section 40 of the Arbitration Act B.E. 2545, arguing it offended public order. The Civil Court refused, and the insurer appealed to the Supreme Court (black case พ.211/2562).

The holding

The Supreme Court dismissed the appeal. Under Section 1557 the parents’ marriage made the daughter a legitimate child from the date of her birth. As a legitimate child she had owed her parents a duty of maintenance, so her death through the tort genuinely deprived the father of support he was legally entitled to. Enforcing the award was therefore not contrary to public order or good morals, and costs of the appeal were waived. The entry is published in the Supreme Court database at deka.in.th.

What makes the decision useful is its sequencing. The accident, the death and the arbitration all preceded the marriage. The court still treated the status as having existed from birth, because that is what Section 1557 says.

Why Backdating Matters for Inheritance and Money

Section 1557 provides that becoming a legitimate child in Thailand takes effect from the date of the child’s birth. It is not forward-looking, and that distinction decides real money.

• Inheritance both ways. A legitimate child is a first-class statutory heir of the father under Section 1629(1), and the father becomes an heir of the child. Without legitimation the traffic runs one way only.
• Maintenance. Section 1564 obliges parents to maintain a legitimate child; Section 1563 obliges the child to maintain the parents. Decision 6436/2562 turns on the second of these.
• Loss-of-support claims. Section 443 allows a person deprived of lawful support by a wrongful death to claim compensation. The claim exists only where a legal duty of support existed.
• Parental power and custody. Legitimation brings the father within Sections 1566 and 1567, so a court can allocate custody between two legal parents rather than confirming the mother by default.

There is a nuance worth holding onto. For succession purposes, Section 1627 already deems an illegitimate child who has been acknowledged by the father to be his descendant, so such a child can inherit from the father without full legitimation. The reverse is not true: the father inherits from the child, and acquires parental power, only once legitimation is complete. Our คู่มือมรดกของประเทศไทยสำหรับชาวต่างชาติ sets out the six classes of heirs in full.

A Legitimate Child in Thailand: What It Changes for a Family

The route to a legitimate child in Thailand is rarely the problem; noticing that it was never taken is. The commonest pattern we see is a foreign father, a Thai mother, a child born before any marriage, and a family that assumes the paperwork is in order because the father’s name appears on the birth certificate. It is not in order, and the gap usually surfaces at the worst moment: a separation, a death, a hospital consent form, or a passport renewal.

Four situations turn on the child’s status. Custody and contact if the relationship ends, which we cover at สิทธิในการดูแลบุตรในประเทศไทย. Enforceable maintenance, explained at child support in Thailand. Thai inheritance, where an unmarried partner and an unlegitimated child are both exposed; the comparison at girlfriend versus wife in Thailand is blunt about it. And immigration, since a Non-O extension based on a Thai child depends on a legal parent-child relationship, not a biological one.

Where a claim against an insurer is involved, the status question and the policy question arrive together. We looked at the second half of that problem in insurance policy limits in Thailand.

Documents and Practical Steps

1. Decide the route. If both parents can marry and want to, the marriage route legitimates the child automatically and needs no separate filing.
2. Gather identity documents: the father’s passport, the mother’s Thai ID card and house registration, the child’s birth certificate and the child’s own ID where issued.
3. For the registration route, expect the district office to summon the mother and the child for consent, and expect a 60-day clock.
4. For the court route, arrange DNA testing early and collect evidence of cohabitation at the probable time of conception.
5. Once legitimation is registered, update the house registration, the child’s records and, critically, any Thai will. Legitimation changes the heirs.

Foreign documents will need certified Thai translation and, depending on the office, legalisation by the Ministry of Foreign Affairs. Allow time for that rather than discovering it at the counter.

คำถามที่พบบ่อย

This article was written and reviewed by Sebastien H. Brousseau, LL.B., B.Sc., who has been based in Thailand since 2004 and has run ThaiLawOnline since 2006. If you need to legitimate a child, respond to a paternity claim, or check how being a legitimate child in Thailand affects a Thai will or an insurance claim, ติดต่อ ThaiLawOnline and we will tell you which of the three routes fits your situation and what it costs.

This article is general information about Thai law and is not legal advice. Court outcomes depend on the evidence and on facts specific to each family, and district office practice varies. Please obtain advice on your own circumstances before acting.