The family of a murdered 17-year-old girl has told 7NEWS it is glad the man accused of killing her is fighting the charges.

Why? Because they want Simon Peter Carman to face the death penalty if found guilty of the charges against him.

The 45-year-old Australian is accused of killing Tunchanok Donhomla in Thailand in June, hiding her body inside a suitcase, and dumping it beside railway tracks just outside the coastal resort city of Pattaya.

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

Carman has pleaded not guilty to all charges and has suggested he acted in self-defence.

“If it wasn’t intentional, then why was she (allegedly) beaten so severely that her face is unrecognizable and badly bruised?” her Donhomla’s aunty Miruntree Thanachai told 7NEWS.

Simon Peter Carman, 45, is accused of murdering Tunchanok Donhomla, 17. Credit: 7NEWS

The Pattaya Provincial Court has now begun considering evidence in the case, with the trial expected to run several months.

Donhomla’s family says it is a good thing he pleaded not guilty because under Thai law a confession could see him spared the maximum penalty — death by lethal injection.

“We are grateful that he has denied the charges and hope he continues to do so, as we want him to face the harshest possible punishment,” Thanachai said.

“The harm he caused us was truly devastating.”

Miruntree Thanachai said the teen’s family are ‘grateful’ the accused has pleaded not guilty, so he can ‘face the harshest possible punishment’ if found guilty. Credit: 7NEWS

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

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 in a suitcase and dumped 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.