Child abduction occurs when a parent takes a child outside the country, often to avoid custody dispute, without the consent of the other parent. There are some dispositions in international law that can be used if you child has been taken from another country to Thailand or from Thailand to another country.
Thailand has ratified The Hague Convention of 25 October 1980 on the Civil Aspects of International Child Abduction. This multilateral treaty is an international convention, wishes to protect children from abduction and harmful effects of retention across international boundaries. You can see on this following link that Thailand ratified this treaty on 14 August 1982. However, it is not because a country ratified a treaty that its application will be strict and efficient. Some parties of this treaty will apply it more slowly and in some others, it could be difficult to enforce even if the country signed the treaty.
The USA GOVERNMENT website specifies that American citizens travelling abroad are subjects to Thai Courts and foreign orders about child custody. (Check this link here). Here is what they write (we underline):
"ENFORCEMENT OF FOREIGN ORDERS: Foreign orders (including U.S. custody orders) are not enforced/enforceable in Thailand. American citizens who travel to Thailand place themselves under the jurisdiction of Thai courts. If a taking parent chooses to remain in Thailand with a child or leave a child behind in Thailand, the U.S. Embassy cannot force either the taking parent or the Thai Government to return the child to the United States. American citizens planning a trip to Thailand with dual national children should bear this in mind."
If your child has been abducted to another country, the first thing you should do is to contact the authorities (police, government offices, embassies, etc.).In many countries, there are some agencies protecting children. Try to get information, as much as you can, so it will help you to make the right choices later.
Once you have contacted the authorities, you might need a lawyer in order to start some legal proceedings on your behalf. You can use Thai Courts and try to get full and sole custody here in order to get back your child if you child is in Thailand. Even if your child is abroad, a clear decision by a Thai court about custody here could help you in another country.