Former Waverley man Adam Lewis Shea, 26, was arrested along with Australian John Edward Cohen, 33, over the alleged shooting of two German tourists in Patong.

Australian National University Research Fellow Tyrell Haberkorn described a legal system most Australians would not recognise.

The Thai legal academic said people could be held without charge for as long as 84 days, remanded in jails where "conditions are pretty horrendous".

Lawyers for the men are expected to apply for bail when they appear before a local judge overnight.

The two men are charged with firing a weapon in a public place with intent to kill.

Ms Haberkorn said most people charged with an offence tended to plead guilty because it led to the automatic halving of any prison sentence.

"You have very few people who enter a plea of not guilty because your chance of being acquitted is pretty slim," she said.

The under-resourced justice system could see defendants wait up to a year to see the inside of a courtroom.

Thailand's image as a safe tropical paradise remained true for most tourists but for visitors "who ran afoul of those belonging to violent entities, it's not a safe place at all".

One legal source, who requested anonymity, said what happened in the period immediately after an arrest was critical.

"Once a case gets to a prosecutor nobody can help, the time for intervention is before any charges are laid," the source said.

They said whatever the Australian government could do behind the scenes may alter the outcome for the two men because there was a "great importance placed on influence" within the Thai justice system.

The source also said the links between Thai police and organised crime was "close".

A classmate of the Tasmanian arrested over a shooting in Thailand said she was shocked to learn about the incident.

The former Queechy High School student described Mr Shea as "a typical guy" at school.

She described him as being "friendly" and "silly" during their four years at Queechy together.

"Our classmates are pretty much shocked really," she said.

The woman said she had kept in contact with Mr Shea via Facebook.