The army has been ordered to recheck the background histories of over 4,000 suspected southern insurgents who took part in a programme aimed at turning surrendered militants into support personnel in the far South after one was implicated in Tuesday's blasts in Pattani.
Fourth Army commander Lt Gen Piyawat Nakwanich issued the order on Friday in the wake of the double bombing at a Big C Supercenter that left at least 61 injured, including four whose condition was listed as critical.
The "Bring People Home" programme was set up by the Internal Security Operations Command (Isoc) in September 2012 and 4,488 former militants have signed up so far.
One of them, Suhaiming Sama-ae, has been linked to the killing of Nuson Khachornkham, a Yala resident whose pickup truck was used to make a car bomb that exploded at the superstore.
Nuson's body was found in a paddy field in Pattani's Nong Chik district on Thursday.
Mr Suhaiming, who was arrested on Thursday night, underwent the programme this February, Lt Gen Piyawat said.
"The programme has been running for five years. I haven't revoked it despite the opposition of Thai Buddhists in the area. But we will closely monitor it," said Lt Gen Piyawat.
Meanwhile, Deputy Prime Minister Prawit Wongsuwon has ordered a ban on steel gas cylinders in the far South and officials are expediting efforts to take care of the matter, Lt Gen Piyawat added.
Isoc spokesman Peerawach Saengthong said more than 4,400 people who underwent the programme will be re-examined. Another 2,312 are due to attend the scheme soon.
"I accept it [the programme] has a loophole as it involves a lot of people, and officials may have failed to check them all thoroughly," Col Peerawach said.
Some militants may have gone along with the scheme to clear their name while others might have been persuaded to return to the insurgency group after graduating, he said.
One of the goals of the programme aims is to persuade insurgents who fled overseas to return to Thailand to fight their charges and work to restore peace and harmony, he added.
But despite the good intentions, the system is open to abuse by militants keen to return to their homeland, one source said.
People with dual citizenship are sometimes admitted to the scheme to make its membership numbers look more impressive but they are not always properly vetted and some relapse into crime, the source added.
The Southern Border Provinces Administration Centre has set aside a budget of 514 million baht for those in the programme to help them find jobs after graduating, give them job training, or provide other help, the source said.
National Security Council secretary-general Thaweep Netniyom said local people in the South have been cooperating with authorities to restore peace by giving information on those suspected of carrying out any insurgent attacks.
This also helps authorities stay abreast of new tactics being employed, he said.
Security officers in the South are now working to track down the suspects in Tuesday's attack. Authorities have identified several suspects in the huge car bombing, officials said earlier. Some evidence has been found against them, they added.
Mr Suhaiming earlier named eight people as being involved in the theft of the pickup truck, including the president of a tambon administration organisation (TAO) in Nong Chik district of Pattani who has already been questioned by the authorities, along with five others.
Gen Thaweep said the TAO president is believed to have been involved in planning the attack.
Pattani special task force chief Maj Gen Jatuporn Klampasut said the investigation is making headway.
Pol Maj Gen Piyawat Chalermsri, the Pattani police chief, said at least 11 people were involved in the bombings. Mr Suhaiming has confessed to jointly hatching the plan, coordinating the robbery and involvement in Nuson's murder, he said.
More than seven people helped plan the attack, Pol Maj Gen Piyawat said, adding that police are gathering evidence to seek arrest warrants.
Prime Minister Prayut Chan-o-cha has asked the public not to share photos or video clips of the bombing.