An Australian man charged with the murder of a 17-year-old girl in Thailand has told her family her dєatᩚh was “out of my control”.

Simon Peter Carman was arrested at Bangkok’s Suvarnabhumi Airport overnight on Friday.

Shortly after, police found a large suitcase that contained a naked body identified as that of Tunchanok Donhomla.

Police retraced Donhomla’s last moments to a Pattaya hotel room she entered with Carman early on Thursday morning.

Carman has been charged with four offences: murder, concealing a body, moving or destroying a body, and taking a minor aged between 15 and 18 for 𝘴єxual purposes.

Police told the ABC that Carman denied all charges, and that he said she “disappeared from the room while I was asleep”.

However, Carman reportedly also told authorities that Tunchanok had threatened him with a knife and he acted in self-defence.

According to Thai media, he said he had not known Tunchanok before they met in Pattaya and went to his condo, and that they initially agreed on a payment of 1,000 baht ($43), but then argued after he offered her 500 baht instead.

Police did not confirm this report to the ABC.

In a video recorded while in custody, Carman addressed Tunchanok’s family and said he felt bad for “what happened to your daughter”.

“It was out of my control,” he said. “I know you’ll be very sad, upset; same-same me.”

“It shouldn’t happen and I hope you’re OK. I know you’re not, but I hope. Um, and please tell other girls to be not – just to be careful”.

The ABC understands Carman is now in detention in Pattaya Prison.

“We believe he killed her, and he is being questioned on suspicion of murder,” said Police Colonel Anek Sarathongyu, Superintendent of the Pattaya City Police Station.

“He has fingernail scratches across his body that are consistent with a struggle, but he denies killing her.”

In a video taken after his arrest, Carman was asked about scratches on his neck.

“I think it’s a spider; they always get in here,” he said.

Police release timeline

The Pattaya City Police Station outlined how its investigation unfolded in an infographic posted on social media.

• Thursday, 25 June, 3:34am: CCTV footage from a condo lobby shows Carman and Tunchanok walking hand-in-hand and entering an elevator.
• Thursday, 25 June, 9:25pm to 9:48pm: CCTV captures Carman dragging a large suitcase out of his room and leaving the condo on a motorcycle with the suitcase strapped to the back. He then sped alongside the railway tracks, disappearing from view for nine minutes.
• Thursday, 25 June, 9:57pm to 10:06pm: CCTV footage shows Carman returning to the accommodation.
• Friday, 26 June, 11:36am: Tunchanok’s friend lodged a missing person report, telling police they had last seen her with a foreign man.
• Friday, 26 June, 2:26pm: Carman is seen leaving his condo.
• Friday, 26 June: Police gather evidence to request an arrest warrant from the Pattaya Court. Officers find Carman’s passport while inspecting a hotel room.
• Saturday, 27 June, 1:15am: Investigative teams from the Pattaya City Police Station and the Immigration Bureau arrest Carman at Suvarnabhumi Airport.
• Saturday, 27 June, 1:30am: Police discover a suitcase near railway tracks about a 10-minute drive from Carman’s hotel, which contains Tunchanok’s body.

The exact timings are unclear, as this timeline contains some discrepancies from previous reports.

A court date will not be announced until police have completed their investigation, which they have 84 days to do.

Australia’s Department of Foreign Affairs and Trade said in a statement to the ABC that it was providing consular assistance to an Australian detained in Thailand.