The Department of Corrections (DOC) has denied that its new regulation, which allows for the detention of inmates outside prison, will benefit convicted former prime minister Thaksin Shinawatra.

Under the new regulation issued on Tuesday, prisoners allowed to be detained outside prison must meet certain requirements.

The venues for detaining them may include houses or buildings with registered addresses.

The DOC on Tuesday said the regulation is intended to categorise inmates and see who should be detained outside prison, such as those who need rehabilitation and career training.

"As for prisoners who are sick, it does not do any good to keep them in prison given the conditions there. It would be better for them if they are detained outside and looked after by their families," the DOC's Sahakarn Phetnarin said.

Asked why he issued the new regulation this week, sparking suspicion that it may benefit Thaksin, Mr Sahakarn said the new rule was long overdue given that the Corrections Act was enacted in 2017.

Thaksin, 74, returned to Thailand on Aug 22 after 15 years of self-imposed exile. However, he was sent from Bangkok Remand Prison to the Police General Hospital that night for health reasons and has remained there since.

Thaksin is not the only convict who has been granted permission to receive medical treatment outside prison for this long, according to the DOC.

Meanwhile, protesters gathered outside Government House to ask Prime Minister Srettha Thavisin to order the authorities to take Thaksin from the Police General Hospital back to prison.