Dual nationality question

The Wife and stepdaughter now have both passports British and Thai. We are arriving in Bangkok August 5th Will Immigration stamp both passports

goronnie wrote:

The Wife and stepdaughter now have both passports British and Thai. We are arriving in Bangkok August 5th Will Immigration stamp both passports

Don't show both passports to Thai immigration. It is not allowed to have dual nationality in Thailand.

Chapter 2. Loss of Thai Nationality.

Section 13. A woman of Thai nationality who marries an alien and may acquire the nationality of her husband according to the nationality law of her husband, shall, if she desires to renounce Thai nationality, make a declaration of her intention before the competent official according to the form and in the manner prescribed in the Ministerial Regulations.

Section 14. A person of Thai nationality, who was born of an alien father and has acquired the nationality of his father according to the law on nationality of his father, or a person who acquires Thai nationality under Section 12 paragraph 2 is required, if he desires to retain his other nationality, to make a declaration of his intention to renounce his Thai nationality within one year after his attaining the age of twenty years, according to such form and in the manner as prescribed in the Ministerial Regulations.

If, after consideration of the said intention, the Minister is of opinion that there is reasonable ground to believe that such person may acquire the nationality of his father or a foreign nationality, he shall grant permission, except in cases where Thailand is being engaged in armed conflict, or is in state of war, he may order the dispensation of any renunciation of Thai nationality.