The family of an inmate yesterday called on the Justice Ministry to launch a probe against Thanyaburi prison warders accused of physically assaulting a 34-year-old inmate during a brawl.
Speaking after lodging a petition with the ministry, Natcha, the mother of the inmate identified only as Krittikorn, insisted her son did not start a fight as claimed by prison officials and demanded an investigation into the incident.
She said he sustained hip injuries and was badly bruised in the assault and did not receive treatment.
Krittikorn is serving a six-year jail term at Thanyaburi District Prison in Pathum Thani for attempted murder.
According to Ms Natcha, the alleged beating took place on Tuesday when Krittikorn, who was trying to intervene in a brawl between prisoners, was beaten with a baton and stomped on by warders.
She said she was confident her son Krittikorn did not start the brawl as she claimed the prison classified him as a "good" inmate.
Krittikorn's wife, Air, said Thanyaburi prison must be held responsible if anything happens to her husband if he is transferred to a higher-security jail.
However, Thanyaburi prison chief Kiattikorn Pattamathat dismissed the brutality allegation, saying Krittikorn had attacked another inmate, prompting the warders to intervene.
He said the incident was captured by security cameras, noting the prison would be ready to share the footage with the family and submit it to the Justice Ministry to set the record straight.
He said an internal inquiry was launched into the incident and the findings should be ready in about a week. He assured the warders would face disciplinary action if found to have used excessive force.
According to Mr Kiattikorn, the inmate might be transferred to a facility with higher security if he fails to behave and continues with attempts to form a gang at the prison.
The Thanyaburi district prison holds about 600 inmates and only has five warders.
On the family's claim that the Krittikorn is classified as a "good" inmate, the prison chief said the inmates are divided into six categories of conduct ranging from excellent to very good, good, fair, bad and very bad.
All newcomers are put in the "fair" category and their conduct is evaluated every six months which can see them switched to good, very good or excellent. Troublemakers are put in the bad or very bad categories.