Lt Gen Manas Kongpan, convicted in the country's largest human-trafficking case, died of a suspected heart attack at the Medical Correctional Hospital on Wednesday night.
Thanakrit Chitarirat, secretary to the Justice Minister, confirmed the death yesterday and said Lt Gen Manas tested negative for Covid-19 in a test earlier that day.
Sources said Lt Gen Manas, a former army adviser and native of the southern province of Nakhon Si Thammarat, had a heart attack while exercising on the eighth floor of the hospital. He was pronounced dead around 8pm.
Manas: Tested negative for Covid
Earlier he had hypertension, high cholesterol and bradycardia and had been admitted to the hospital.
His body was sent to Police General Hospital for an autopsy. His funeral rites would be held at Wat Chonprathan Rangsarit in Nonthaburi province from today to Sunday.
Mr Thanakrit said Lt Gen Manas was sent to the hospital because he had underlying health conditions. However, the official cause of death would be released by the Institute of Forensic Medicine.
According to Mr Thanakrit, the eighth floor of the hospital is arranged for inmates in their senior years to take exercise and recreational activities.
Lt Gen Manas, 65, was among 103 people convicted for their role in the trafficking of Rohingya migrants to jungle camps in the South. It is believed to be the country's biggest human trafficking case ever tried in court.
He was found guilty of several offences involving trafficking and taking bribes.
The defendants were arrested in a massive crackdown following the discovery of more than 30 graves in May, 2015 on Khao Kaew mountain in tambon Padang Besar in Songkhla's Sadao district near the Thai-Malaysian border.
The bodies, found close to a makeshift camp, were suspected to be Rohingya Muslim migrants who were possibly victims of human trafficking.
There was insufficient food and water at the camp where the detainees were kept. The detainees were not allowed to use phones and were threatened if they tried to contact anyone.
In November 2019 the Appeal Court increased the prison terms in the mass Rohingya graves case. For some defendants, including Lt Gen Manas and several local southern politicians, the sentences were quadrupled to around 80 years.
Under the ruling, Lt Gen Manas's term was increased from 27 to 82 years.