A 32-year-old insurgent suspect found unconscious while in custody at Ingkayutthaboriharn military camp in Pattani died on Sunday morning after a month of lying in a coma, prompting calls for an inquiry into the incident.
Songklanagarind Hospital, where Abdulloh Esormusor was admitted in July, said he died at 4.03am as a result of severe pneumonia and septic shock.
The hospital said Abdulloh's condition had been stable until Friday night when doctors diagnosed inflammation of the lungs and abnormal gas exchange for which he was administered antibiotics and high-concentration oxygen.
His condition worsened on Saturday night after the onset of dangerously low blood pressure did not respond to treatment, according to the hospital.
The case has prompted allegations of human rights abuse by security authorities and a lack of transparency in the criminal investigation process against insurgent suspects in the restive South.
When the incident was first reported, the Internal Security Operations Command (Isoc)'s Region 4 Forward Command said no evidence had emerged to suggest the suspect's collapse had resulted from soldiers' actions and the man had undergone a medical check-up which confirmed he was fit to be interviewed.
The Fourth Army Region has launched two probes into the incident; one looking into security officers' role to determine if they were in the wrong and another to establish the facts to ensure transparency.
Abdulloh was the head of a family taking care of his 60-year-old mute mother. He and his wife had two sons, 7 and 2 years old.
He was arrested at his home after being implicated in insurgent activities in Sai Buri district in Pattani by a leading insurgent named Ibroheng Maseng. He was then brought to the Ingkayutthaboriharn camp for questioning where he was found unconscious several hours later.
It is not known what happened to make him fall unconscious after being brought in for questioning.
Abdulloh was rushed to the camp hospital which provided first aid before referring him to Pattani General Hospital and Songklanagarind Hospital in Songkhla's Hat Yai on July 22.
According to doctors, he was suffering from cerebral oedema, or brain swelling, which could have been caused by a lack of oxygen, among other things.
Future Forward Party list-MP and spokeswoman Pannika Wanich on Sunday called on authorities to establish the facts behind Abdulloh's death and release the findings to the public.
According to Ms Pannika, the government would be grilled over the incident when the House convenes its next meeting.
"There have been other incidents, not just this one, and several people were left disabled or dead. The public pays little attention to these cases in part because they think these people were detained because they might have done something bad.
"But let me say these people are detained without due process. It's time to pay more attention to issues in the deep South," she said.
Pramote Prom-in, spokesman of Isoc's Region 4 Forward Command, on Sunday defended the army's treatment of suspects and its processes, saying he welcomed independent investigations.
Col Pramote insisted there were explanations for the incident.
Angkhana Neelapaijit, a former member of the National Human Rights Commission, called on the army to audit its interrogation process to ensure there are no hidden forms of abuse.
"Wounds or no wounds isn't the point. If we're aware of the UN's definition of torture, we know that physical signs are not necessary," she said.
"Based on complaints we have received, sleep deprivation is often used and it doesn't show," she added.
Abdulloh's family submitted a petition to Prime Minister Prayut Chan-o-cha on Aug 7 in Yala demanding the truth of what happened.
His body was collected by his family and brought back to Pattani for burial.