Natthaphol Thavornphibun, the prime suspect in the murder of a 15-year-old boy at a tutorial school in Nakhon Sawan province, has admitted hitting the boy with a baseball bat more than 20 times, a police source said.
The beating caused severe injuries that led to the boy's death.
Mr Natthaphol, owner of the tutorial school that prepared boys looking to enter the military academy, beat the boy as a punishment for swearing after Mr Natthaphol's mother-in-law refused to return the boy's mobile phone when he asked for it, said the source, citing findings from a police investigation into the case.
It wasn't the first time Thapakorn "Nong Chaidaen" Sapsin was beaten with a baseball bat while at the school, said the source.
Each week, Mr Natthaphol allegedly staged a beating session called "expiation", in which he gave a baseball bat to each of the boys at the school and told them to hit someone who did something wrong or anyone who they simply wanted to hit, said the source.
Thapakorn was hit on several occasions during the weekly beatings, said the source.
He was an only child and died after being rushed to a hospital after being beaten last week.
While staying at the tutorial school, students were not allowed to use a phone and had their mobile phones taken away, the police source said.
Their parents were required to make an appointment when they wanted to see their children.
Other boys who witnessed the fatal beating were allegedly threatened by Mr Natthaphol to never tell police or anyone what happened.
Some, however did so during questioning, said the source.
Bloodstains found at the scene as well as in Mr Natthaphol's car are being treated as evidence, as are eight baseball bats police retrieved after Mr Natthaphol and other students allegedly dumped them underneath a bridge crossing the Ping River.
One of the retrieved bats had Mr Natthaphol's name on it.
As for burn marks found on the boy's body, they were caused when Mr Natthaphol ordered some boys to hold Thapakorn down and set light to his pubic hair, the source said.
Mr Natthaphol, his wife, Phiraya Phalasaen, and mother-in-law Nonglak Phalasaen, have been charged with colluding to abuse Thapakorn and now are being held in Nakhon Sawan prison. They have denied any wrongdoing.
Nakhon Sawan governor Atthaporn Singhawichai said an investigation found Mr Natthaphol's tutorial school was an illegal one.