The marriage in Thai law can be valid only if the parties are 17 years of age and none of them is spouse of another person .If the girl is still a minor, she have the consent of her parents who may give it to her in writing otherwise the parents are entitled to cancel the marriage. If They are mature, they can marry without the parents consent But neither of them is spouse of another person if she younger than 17,she has to apply for permission of court and marriage is valid only by registration with the Thai administrative authorities unless they go home to marry according to the foreigner law.