Australian man Simon Peter Carman has spoken publicly for the first time since being locked inside a Thai prison, insisting he is innocent of murdering a 17-year-old girl and claiming he acted in self-defence.

The 45-year-old Perth man has been detained at Pattaya Remand Prison for almost two months following the death of Thai teenager Tunchanok Donhomla, who was known to family and friends as “Cake”.

Speaking to the ABC’s Foreign Correspondent in a private visitors’ room at the prison, Carman said he was hoping to be released and maintained he had done nothing wrong.

“I’m hoping and praying that I get released,” he said. “I have not done anything wrong. I shouldn’t be here … I do not understand what’s going on.”

Carman faces four charges, including murder, concealing a corpse and abducting a minor for indecent purposes. He has pleaded not guilty to all charges and could face life imprisonment or the death penalty if convicted of murder.

Thai police allege Carman met Tunchanok on Pattaya’s Beach Road in the early hours of June 25 before the pair returned to his accommodation.

CCTV footage reportedly shows the pair walking hand-in-hand into the building. Later that night, footage captured Carman dragging a large suitcase from the building and transporting it on a motorcycle.

Two days later, Tunchanok’s body was discovered inside a suitcase dumped near railway tracks around a 10-minute drive from Carman’s accommodation. Carman was arrested at Bangkok’s Suvarnabhumi Airport while attempting to board a flight to Perth.

In his first account of what he claims happened inside his room, Carman told the ABC he had met Tunchanok while she was with two friends and said she subsequently followed him home.

He said he did not know she was 17, claiming he believed she was aged somewhere between 25 and 35.

According to Carman, an argument over money then escalated into a violent confrontation.

He claimed he gave Tunchanok 500 baht – about $21 – before she demanded more money and produced a knife.

Carman said he repeatedly asked her to put the knife down as the pair struggled, before she eventually “went limp”. He said he did not call an ambulance or police because he did not trust the authorities.

“I feel deeply sad. I obviously wish it never happened, but it was unavoidable,” Carman said.

“All I was trying to do was restrain her from stabbing me.”

Carman also told the ABC he does not yet have a lawyer and said his only visitors in custody have been Australian embassy officials.

His version of events will now be weighed against evidence gathered by Thai investigators.

Police say an autopsy found Tunchanok died from suffocation and suffered a brain injury. Investigators also say Carman’s DNA was matched to DNA found on the teenager’s body.

Pattaya Police Colonel Anek Srathongyoo said investigators would submit the case file to prosecutors on Monday, with prosecutors having until September 18 to decide whether to indict Carman.

Tunchanok’s devastated father, Thongchai Donhomla, has called for the harshest possible punishment if Carman is convicted.

“I don’t ask for much. I just hope my child gets the justice she deserves,” he said.

The prison interview was a rare one, with the ABC reporting it was the first foreign news organisation in at least 15 years to receive permission to interview a foreign inmate inside a Thai prison. Prison officials were permitted to review footage for security reasons, while discussion of prison conditions was prohibited.

Images: Pattaya Police