A school deputy director in Bangkok has been accused of sexually abusing her 12-year-old student and threatening to make public explicit photos and videos if the girl did not comply.

The student, enrolled in Grade 6 at a school in Bangkok's Nong Chok district, filed a complaint Tuesday at Nong Chok police station. She also presented chat messages between her and the accused as evidence to Pol Capt Chaiwat Charasmethawit, deputy investigation chief.

The girl was escorted to the station by social media activist Guntouch Pongpaiboonwet, alias Gun Jompalang. 

Mr Guntouch said the girl's mother and elder sister sought his help after learning of the alleged sexual abuse.

The 38-year-old former teacher, now a deputy director at another school, is alleged to have lured the girl into sending her naked photos.

The teacher later threatened to send the explicit photos to the media if the victim did not comply with her demands, according to the activist.

"In my view, individuals engaging in such behaviour do not deserve to be teachers. Despite being married and living with her husband, she still lured the student into a sexual act at a petrol station," said Mr Guntouch. "It's an evil and immoral act."

The accused teacher also allegedly claimed connections with influential figures and politicians in order to discourage the girl from reporting the offences. 

Mr Guntouch said there must be an investigation to find out whether the accused had committed similar offences against other students.

The alleged sexual abuse came to light when the victim informed her family about the teacher's threats to disseminate the explicit photos and videos.

Police said they would call a psychologist and concerned agencies to jointly question the girl about the matter before considering a warrant to summon the accused to acknowledge the charges.