The men were arrested and were expected to appear in Phuket Provincial Court on Monday.
They face multiple charges including bribery, robbery and obstructing police.
Law Aid International director and barrister Craig Tuck said after their court appearance they were likely to be detained further.
“The court has the jurisdiction to grant further remands and those remands can be up to 84 days in total,” Tuck said.
“It is unlikely that any criminal justice system would release or deport people prior to dealing with them within the criminal justice system that’s in that country, so they will be subjected to the court processes in Thailand.”
The conditions the men would face while going through the Thai judicial system depended on where they were placed, but cells were known for being overcrowded, Tuck said.
“I certainly know of situations where these cells were so crowded that people had to take turns sleeping at night because not everybody could lie on the cell floor.”
If the men were sentenced, Tuck expected they would continue to be detained in a Thai jail
“That’s part of the rule of law, fair trial in countries dealing with those people that breach the penal code within that jurisdiction.”
A Ministry of Foreign Affairs and Trade (MFAT) spokesperson said consular officials were providing assistance to the family of two New Zealanders.
“The ministry is unable to comment further due to privacy reasons.”
Tuck said the role MFAT played while the men faced the judicial system was to provide social and humanitarian support.
“They do not engage in another country’s criminal justice.”
MFAT had a list of local lawyers they could provide the men with. “Often those lawyers are just involved in the commercial, not criminal, jurisdiction and many times people are left to navigate criminal justice or criminal law in whatever countries are detained in, in a trial-and-error fashion.”
The parents of the two men charged said they were “understandably distraught”.