Mr Ayut said Wisut, a former gynaecologist at Chulalongkorn Hospital, was released on Monday morning after having served 10 years, seven months and 25 days in prison.
According to Mr Ayut, after being sentenced by death by the Bangkok South Criminal Court in 2003 Wisut had his sentence reduced on many occasions under a royal pardon because he had performed good deeds by taking care of and providing treatment for sick inmates at Bang Khwang prison until he had less than five years left to serve in jail.
He subsequently met the criteria required to be freed on parole.
As recommended by a review committee, the prison submitted a proposal for Wisut's parole to the Corrections Department for consideration. The proposal was approved by a committee of the department, leading to his release today.
The actual date for Wisut to complete his remaining jail term is Sept 24, 2017. From now until that day, Wisut is required to regularly report to the Probation Department.
Mr Ayut said Wisut had earlier told him if he was released he would like to work for the benefit of society if he was allowed to, but did not say how he would actually lead his life after being freed.
Prisoners freed on parole can be returned to prison to serve out the remaining time if they violate conditions set for their freedom.
He said said total of 14 prisoners were released at the same time as Wisut.
His release on parole came six years after the Supreme Court upheld the death sentence against him on July 25, 2007.
In 2003, the Bangkok South Criminal Court sentenced him to death for killing his wife, dismembering her body and covering up the murder from Feb 20-March 23, 2001.
The court ruled that although there were no eyewitnesses able to confirm the grisly murder, there was strong scientific and circumstantial evidence, including conflict between the couple and Wisut's forging of his wife's leave letter around the time she disappeared. There was convincing evidence that Wisut had lunch with Dr Phassaporn, then took her to a Chulalongkorn University dormitory, killed her, dismembered her body and flushed the remains down toilets at the dormitory and at Sofitel Central Hotel in Lat Phrao on Feb 20-21, 2001.
Although no body was found, the court determined Dr Phassaporn must be dead. DNA tests of pieces of human flesh weighing up to 3.3kg found in septic tanks and bloodstains in the water pipes and bathrooms of Wisut's dormitory and hotel rooms matched those from Dr Phassaporn's hair and her father.
The Appeals Court upheld the lower court's verdict.