Imprisoned former commerce minister Boonsong Teriyapirom followed prison protocol before being given permission to attend his mother's funeral in Chiang Mai, said Wuttichai Jenwiriyakul, director of the Klong Prem Central Prison.
The prison chief was on Tuesday responding to public queries sparked by an image of Boonsong out of prison and joining his family at his mother's funeral rites.
Boonsong is currently serving a long prison term for his involvement in the bogus rice deal under the Yingluck Shinawatra administration.
Mr Wuttichai said that Boonsong was eligible to apply for prison leave.
The former commerce minister had properly requested the leave and attached his mother's death certificate with the required paperwork.
After he reviewed the request and found everything was in order, he granted the request for Boonsong to leave the prison from Sunday to Monday.
On Sunday night, Boonsong was transported to a prison in Lamphun where he spent the night. Lamphun is Chiang Mai's neighbouring province.
The next day, he was escorted to the funeral rite. After the ceremony ended, Boonsong travelled back to Klong Prem prison in Bangkok.
Mr Wuttichai said a similar request was approved for red-shirt leader Nattawut Saikuar, who was also serving time at Klong Prem, to attend his father's funeral.
Justice Minister Somsak Thepsutin said the Corrections Department was authorised to approve the leave and that Boonsong has not served out his jail term.
Boonsong, who was sentenced to 48 years in jail by the Supreme Court over bogus government-to-government rice deals, has had his term reduced to 10 years and eight months.
He is due to be released from prison in April 2028.
