The Corrections Department on Thursday reported nearly 8,000 people released from prison on parole had undergone health checks, as human rights activists called for more leniency toward eligible inmates.
The department said 7,890 people were gradually discharged from prisons since October in a bid to alleviate overcrowding in the kingdom's prison system.
The kingdom then experienced an outbreak of Covid-19.
Even though there have been no reported cases of inmate transmission, 18 people who worked with the chief of Nakhon Nayok Provincial Prison were placed under a 14-day quarantine period after he tested positive for the novel coronavirus.
Corrections Department chief Pol Col Naras Savestanan said those who were released on parole passed their health checks, among other criteria to be granted clemency.
Inmates are eligible for parole when they have served two-thirds of their prison term and demonstrated good behaviour. Inmates aged 70 or older who have served one-third of their sentence are also eligible.
"We did not release them all at once, we did so gradually," Pol Col Naras said.
The first batch, which consisted of 1,261 people, left prison in October and similar numbers of inmates were discharged each time since.
Pol Col Naras said those on parole must periodically report to the authorities until their jail term ends, adding if they did not, parole would be withdrawn, and they would return to prison.
Nikon Wisaphen, chairman of the Union for Civil Liberty, said Prime Minister Pratyut Chan-o-cha should consider releasing more inmates as a measure against the spread of Covid-19.
Mr Nikon said parole hearings should be held for inmates with one year in prison left, the elderly who are above 60, cancer and heart disease patients, pregnant women and those who committed minor offences.
The number of inmates serving jail terms of less than one year is at about 139,000 across all prisons in the kingdom. They represent the largest grouping of all inmates, according to the Thailand Institute of Justice.
At least 153,800 inmates should be released on parole, said TIJ chief Kittiphong Kittayarak.
The national Covid-19 figure stood at 2,672 as of Thursday.
