An Australian man accused of murdering a Thai teenager and stuffing her body in a suitcase has pleaded not guilty to all charges against him during his first appearance in court.

Simon Peter Carman, 45, was arrested over the death of Tunchanok Donhomla, 17, in the resort town of Pattaya in June.

Authorities charged him with four offences, including murder, concealing a corpse, and abducting a minor.

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He appeared before the Pattaya Provincial Court in Thailand on Friday and pleaded not guilty to those allegations, claiming he was acting in self-defence.

Carman’s next court appearance is on October 12.

Simon Peter Carman, 45, is accused of murdering Tunchanok Donhomla, 17, in the bustling resort city of Pattaya. Credit: 7NEWS

Carman allegedly met Donhomla, known locally as “Cake”, in Pattaya, about two hours south of Bangkok.

CCTV footage allegedly showed the pair holding hands as they entered his apartment.

Police said Carman was later seen wheeling a large suitcase out of the building before strapping it to the back of a moped and riding away.

The teen’s body was found stuffed dumped in a suitcase near train tracks.

Pattaya City Police said autopsy results showed Donhomla suffered a brain injury and died of suffocation.

Carman was arrested at Bangkok’s main international airport, allegedly trying to board a Jetstar flight to Perth, before being charged.

If found guilty, he faces life in prison or the death penalty.

7NEWS understands Carman had previously worked as truck driver and moved to Thailand in 2025.