A high school in Lampang is under investigation after a student was caught selling cannabis to her classmates, the Office of the Basic Education Commission (Obec) said.
The Mathayom 6 (grade 12) student attended Hang Chat Witthaya School in Hang Chat district.
She sold dried and liquid forms of cannabis to other students.
The students would go into class feeling drowsy and unable to concentrate on their studies, said Pairoj Lohsunthorn, Pheu Thai Party MP for Lampang's constituency 2, who was told of the problem.
The school's director, Jaichai Punnapong, confirmed the report. He said the school has filed a police complaint against the student who peddled the drug on school premises.
Her parents were invited by police to acknowledge their daughter's offence.
The director of the 500-student school reiterated the Education Ministry's policy to keep cannabis out of schools and prohibit its consumption on school grounds.
Mr Jaichai said the school had now implemented strict measures against bringing cannabis into the grounds;.
Teachers now check to make sure students are not in possession of cannabis or other banned substances before they enter the school. Their bags are searched.
The school is off-limits to unauthorised vehicles. Parents drop their children off outside the school.
Mr Jaichai denied parents' criticism that the school had been lax in its care of students.
Chanthana Wongkham, head of the school's student activities, said the student was caught selling cannabis on several occasions.
Her parents had since decided to move her to another school, Ms Chanthana said. Hang Chat School decided not to dismiss her as it wanted to give her a second chance.
Obec secretary-general Amporn Pinasa said he has ordered an investigation into the school.
The office was checking to see if the school has taken any action over the incident. The Education Minstry had previously issued a detailed announcement banning cannabis from schools nationwide.
"Schools are supposed to comply strictly with the announcement," Mr Amporn said. The investigation would reveal whether Hang Chat Witthaya School executives acted negligently in allowing the sale of cannabis.
In Chaiyaphum, three people were taken to hospital after consuming cannabis in Phu Khieo and Chatturat districts, provincial public health officer Wachira Botpibul said.
The first two cases were admitted to Phu Khieo Hospital. They had smoked cannabis and subsequently experiencing seizures.
The third person, with a history of psychiatric treatment, hallucinated after eating a meal cooked with cannabis.
