Thailand: Dual and Multiple Citizenship

Constitutional safeguards and the Thai Nationality Act confirm that Thai-born citizens cannot lose their nationality and that dual citizenship is legally accepted. 

1. Constitutional Framework

The 2017 Constitution of Thailand provides an important safeguard in Article 39:

“No person of Thai birth shall be deprived of Thai nationality.”

This means that Thai nationals by birth cannot lose their nationality merely by acquiring another one. The constitutional protection prevails over any conflicting statutory provisions. In particular, it dispels the common misconception that Thai–foreign dual nationals must choose one nationality upon reaching adulthood. There is no legal “option obligation” in Thailand.

2. Statutory Provisions – Thai Nationality Act (Consolidated 2021)

In addition to the Constitution, the consolidated Thai Nationality Act sets out the rules on the acquisition and loss of nationality:

1. Acquisition by birth (§ 7): A child automatically acquires Thai nationality if at least one parent is Thai, regardless of whether the child is born in Thailand or abroad.
2. Naturalisation on application (§§ 9–10): Foreign nationals may apply for Thai nationality if certain conditions are met, including legal majority, at least five years of lawful residence with permanent residence status, stable income, good conduct (i.e., no criminal record / good moral character), and sufficient command of the Thai language.
3. Facilitated naturalisation through marriage (§ 11 (4)): Men married to Thai citizens benefit from eased conditions, such as a shorter residence period or reduced language requirements.
4. Procedure (§ 12): Applications are filed with the competent authorities. The final decision rests with the Minister of Interior. Naturalisation requires royal approval and is published in the Government Gazette.
5. Loss of nationality (§§ 15 ff.): Nationality may be lost through express renunciation, voluntary acquisition of the nationality of a hostile state, or fraudulent statements during the application process. However, these provisions are practically irrelevant for persons of Thai birth, as Article 39 of the Constitution protects against deprivation. For naturalised citizens, loss may occur only in exceptional cases (e.g., serious crimes or threats to national security).

3. Developments since 2021

In recent years, Thailand has modernised and liberalised its nationality law:

1. Recognition of dual nationality: While dual nationality was previously tolerated but sometimes viewed critically, the 2021 consolidation clarified that acquiring a second nationality does not automatically lead to the loss of Thai nationality. Likewise, foreigners naturalising as Thai citizens are not always required to renounce their original nationality.
2. Policy and administrative reforms: Since 2021, the government and the Ministry of Interior have advanced initiatives to facilitate access to Thai nationality. Prominent examples include the naturalisation of long-term resident minorities and stateless children. For typical dual-nationality cases – such as Thai–foreign families – current practice confirms that Thailand accepts dual nationality, provided no abuse is involved.
3. Practical clarification: The long-standing assumption that dual-national children must elect one nationality at age 20 is now outdated. Neither statutory law nor administrative practice requires such a choice.

4. Practical relevance for Thai–Foreign cases

For Foreign clients and their families, the current legal framework entails the following:

1. Naturalisation without renunciation: Foreign nationals may acquire Thai nationality without being required to give up their Foreign citizenship.
2. Children with dual parentage: Children with one Thai parent automatically acquire Thai nationality while retaining their Foreign nationality. They are not required to make a choice in adulthood.
3. Rights and benefits in Thailand: Dual nationals enjoy the full rights of Thai citizens – including land ownership, access to regulated professions, residence and work rights, and access to education.

In sum, Thailand has in recent years moved towards a more inclusive citizenship policy, which brings clear advantages for bi-national families.