"Although Thailand's age of consent is usually said to be 15, the laws can be interpreted to allow prosecution for sex with someone under 18."
http://www.avert.org/age-of-consent.htm
"The age of consent in Thailand is 15 (with the below caveat) as specified by article 279 of the Thai Criminal Code. The current legislation applies to all regardless of gender and/or sexual orientation, although it is a common misconception that it applies only to women.[citation needed]
"However parts of the Prevention and Suppression of Prostitution Act which disallow any sexual contact with prostitutes under the age of 18, are widely interpreted by some local authorities to cover sexual acts classed as "obscenity for personal gratification". Also from the Penal Code Amendment Act of 1997 Section 283bis, having sex with a child under 18 is a compoundable offense even with the consent of that person. The parent or the child may file charges against the other side if he or she later regrets his or her own action. This ostensibly makes the Thai unfettered age of consent 18.
"A high profile example of this application of the law was a statutory rape charge filed against the lead singer of the Thai band Big Ass for allegedly having had sex with a (then) 16 year old girl. The charge was filed by the girl after the singer refused to take responsibility for her baby. The singer has since been cleared of being the baby's father due to the results of a paternity test and he received 2 years suspended sentence.[30][31]
http://en.wikipedia.org/wiki/Ages_of_consent_in_Asia#Thailand