An alleged Thai separatist, who died in hospital following his interrogation by the military, has been laid to rest in his hometown in Pattani province as calls grow for an investigation into his death.

Abdulloh Esormusor died on Sunday after 35 days in a coma following reports of torture while he was in custody. His death comes as warnings of violence in the restive southern province increase.

On Tuesday, Thailand’s opposition Future Forward Party (FFP) called on the government to conduct an autopsy on Abdulloh’s body.

In a statement on its official Facebook page, FFP said it is the “duty of all those involved” to answer questions about the circumstances leading to Abdulloh’s detention and death.

The death of Abdulloh “puts the credibility of General Prayut and Thai military leaders on the line,” Sunai Phasuk, senior researcher on Thailand at Human Rights Watch (HRW), said, referring to Thai Prime Minister Prayut Chan-ocha by his military title.

“The military-led inquiry is hogwash and fails to give any confidence that there will be justice. So far, it has been unable to answer even the most basic questions about Abdulloh’s treatment at the interrogation centre, and what were the methods soldiers used to interrogate him before he fell into a coma,” Sunai told Al Jazeera.

At his funeral on Sunday, relatives and friends carefully carried Abdulloh’s body from his home to the local mosque in the Sai Buri district of Pattani province.

Images posted online showed a crowd of people bidding their final farewells to the man, who was taken by the military from his residence on July 20.

Sunai of HRW told Al Jazeera that suspected separatist rebels from the pro-independent group Barisan Revolusi Nasional, also attended Abdulloh’s burial, likely establishing his links to the armed fighters.

Those who knew him told HRW that before his detention, 34-year-old Abdulloh had been the caretaker for his 60-year-old mute mother, as well as his wife and their two children.

Alleged ties to separatists

According to reports, Abdulloh was taken by authorities after a suspected armed fighter claimed he was involved in separatist actions.

At the time of his detention, he was not facing any charges.

Abdulloh was then interrogated at the 43rd Taharn Pran Task Force centre, located within the notorious Ingkayutthaboriharn military base.

Abdulloh was left in a coma for 35 days before he died on Sunday [Tuwaedaniya Meringing/AFP]

The Internal Security Operations Command (ISOC) reported that the investigation lasted until late that night.

At about 3am the next day, soldiers reportedly found him lying unconscious on the ground.

He was then rushed to Pattani General Hospital, then transferred to Songklanagarind Hospital in neighbouring Songkhla province the next day.

According to medical reports from Pattani General Hospital, Abdulloh was in a coma due to severe brain swelling as a possible result of lack of oxygen to the brain. He died on August 25.

Abdulloh’s alleged ties to separatist groups were never clearly established.

“By relying on repressive measures to battle separatists, Thai authorities have created a fertile ground for the insurgency to expand and become further radicalised – precisely the opposite of what they intend,” said Sunai of HRW.

“Will they [military] allow a cover-up, or will they ensure that rogue officers in the ranks will be brought to justice?”

The military said that they are conducting an investigation into the events that led to Abdulloh’s coma.

Pramote Prom-in, spokesman for the military’s internal security operations command in southern Thailand, called on the public to allow the official inquiry to publish its results, according to Reuters.

In a recent statement, Prime Minister Prayut dismissed the allegations of torture.

“You said he was tortured. He was examined by doctors and they did not find anything. He just fainted. He fainted after he was arrested. Do you watch movies too much?” he said.

Simmering conflict

Conflict has been simmering for decades in Thailand’s deep south, which is predominantly populated by Muslims of Malay background.

Tensions escalated in 2004 after a series of well-planned attacks on police and government facilities. Since then, there have been over 7,000 deaths resulting directly from the conflict. Most of the deaths have been civilians.

Although violence in the area has been on the decline for several years, the last three months have been a different story.

A month ago, armed fighters attacked a checkpoint by simultaneously bombing and shooting a guarded roadblock. The attack left four military personnel dead. It was the deadliest attack in the region since January.

Experts warn that the recent death of Abdulloh will only likely result in more violence.

“I think a spike in violence is inevitable,” Zachary Abuza, a specialist on the Thailand conflict and professor at the National War College in Washington, DC, told Al Jazeera.

Matt Wheeler, a senior analyst at the International Crisis Group, said that a portion of the local population in Pattani and other areas in the south, “has long been resentful of the Thai military’s presence and security measures.”

“Abdulloh’s death in custody is a reminder that zealous counterinsurgency efforts too often result in human rights abuses, which in turn play into militant narratives and deepen distrust between many Malay Muslims and the Thai state,” Wheeler told Al Jazeera.

Meanwhile, Abuza also told Al Jazeera that, based on numerous interviews he conducted with ex-detainees in the southern region, he found that almost all of them had been tortured to one degree or another.

There have been over 7,000 deaths resulting directly from the conflict in southern Thailand [File: Stringer/EPA]

“This is part of the Thai military culture that no one in leadership seems willing to take on,” he said.

This is not the first time that a detainee has been allegedly tortured while being interrogated by the military.

In 2016, another alleged southern separatist, Rohana Salilatae, was detained and allegedly tortured while in military custody.

In 2015, Prathin Chanket, 60, alleged that he was abused for two days for supposedly plotting an attack on the Prime Minister.

In 2014, “Red Shirt” activist Kritsuda Khunasen, 27, claimed to have been tortured while under interrogation as well.

For the past 15 years, not a single military personnel has been prosecuted for alleged torture and rights abuses, according to rights groups.

Now, the country can only wait and see if the violence will worsen – as Abdulloh’s death has added fuel to the flames that have long made the situation in the region combustible.