Police say his sudden departure was under more sinister circumstances, particularly after he emerged as a suspect in a fatal shooting in Sydney's inner-west.

On Tuesday the law finally caught up with the 28-year-old gym owner.

A Thai court sentenced Bagnato to the death penalty for the murder of Hells Angels heavyweight Wayne Schneider in late 2015.

Schneider, a well-known criminal figure in Australia who was involved in major drug trafficking before his death, was bashed, bound and buried outside the Thai tourist town of Pattaya.

After a days long manhunt, police arrested friend turned foe and Sydney inner-west kick boxer Bagnato.

Bagnato was already wanted back home in Australia for questioning over the alleged murder of Bradley Dillon, 25, in Leichardt in August, 2014.

In January 2016, a warrant was issued for his arrest in case he ever stepped foot back in the country.

It is understood Bagnato left Australia not long after Mr Dillon's death.

In November 2015, Bagnato was accused of kidnapping Schneider from his luxurious villa, breaking the heavyset bikie's neck and shoving his body into a rental vehicle.

Unfortunately for him, the car had a GPS tracker on it that led police to a grave outside of Pattaya.

Bagnato left Thailand with his wife and crossed the border in to Cambodia before he was eventually arrested.

In a 40-minute judgment in Pattaya on Tuesday, a judge found Bagnato guilty of murder and sentenced him to death.

The judge said DNA and blood evidence placed Bagnato at the scene of the crime and weapons used during the assault were prepared beforehand.

He was handed a fatal sentence as relatives watched on from inside the court.

American Tyler Gerard, 22, was charged with a lesser offence and received a two-year suspended jail sentence.

Australian man Luke Hunt has already been convicted of aiding and abetting Bagnato by driving him and his family to the Cambodian border.

Hunt was sentenced to three years jail, suspended for two years after pleading guilty.

Bagnato, who fought under the name "Tony Bang", was partners with Schneider in a boxing gym in Sydney.

Bagnato was seen as a rising star on the muay thai scene and trained at a gym in the city's south.

He was hailed "the next big thing" after winning several fights before he left Australia and fought under the Saint Michael Fight Club banner.

But it was his move towards the drug trade in Sydney that saw him kicked out of the secretive group, former associates said.

His involvement in the fight club attracted the focus of the homicide squad investigation into Mr Dillon's death.

Some of the club members and alleged associates, including ex-boxing champ Jeff Fenech, were hauled before the NSW Crime Commissioner to answer questions about the group and what they knew of Mr Dillon.

That case is still before the courts.

Schneider was an influential player in the drug market between Australia and Europe, acting as a conduit between buyers back home and suppliers overseas.

Fairfax Media understands detectives attached to one particular investigation running out of NSW were planning to travel to Thailand to arrest Schneider over his drug activity.

But their plans were thwarted when he was killed.

According to the ABC, Bagnato denied killing Schneider, claiming he spent the night of his death dining with former Commanchero bikie gang president Amad "Jay" Malkhoun, before meeting up with a Thai woman.

Bagnato's family declined to comment on Tuesday.