The discovery raises serious questions about how the cameras were able to be installed and remain undiscovered, potentially for years.
The Department of Foreign Affairs and Trade (DFAT) confirmed that a former locally engaged staff member at the Australian embassy in Bangkok was arrested by Royal Thai Police on January 6.
The ABC understands the former employee, Bank Thamsongsana, has dual Australian and Thai citizenship and was until recently employed as an IT systems manager at the embassy.
His recently deleted LinkedIn profile stated he had been employed by DFAT since 2013, after living and studying in Australia and holding several other Australian government positions.
It is understood multiple cameras were discovered directed at women's showers and toilets after an SD card containing images of female staff was found on a bathroom floor last year.
A government employee with knowledge of the incident told the ABC employees at the embassy were shocked and shaken.
"Female staff, Thai and Australian, are very anxious," the person said.
"Some of the women don't feel safe to stay there. They feel compromised and threatened."
The government employee added that embassy staff wanted more support to "manage the serious psychological impacts of this matter, or even the possibility of serious security breaches".
It is not known how long the cameras had been in place or how much vision had been collected but it is understood dozens of Australian embassy staff are assisting the Thai police.
An officer from the Royal Thai Police, who is working on the investigation, told the ABC it was "a sensitive case" that "involved many people".
The officer said forensic investigators were currently looking through the evidence and female police would be interviewing the women affected.
Police confirmed a man had been charged with two offences under sections of the Thai criminal code which cover sexual and public nuisance offences.
The charges carry a maximum penalty of 10 years' jail or a 20,000 baht ($850) fine.
The ABC has been told Mr Thamsongsana, a married man in his 30s, was released on bail after spending one night in custody.
The Australian Federal Police and DFAT declined to comment on whether there would be any Australian government or law enforcement investigation into the incident.
'This is supposed to be a secure government building'
The Australian Embassy in Bangkok is one of Australia's largest diplomatic missions in the world.
Peter Jennings, executive director at the Australian Strategic Policy Institute, said the security breach was a matter of great concern.
"There's clearly been a failure here on a number of levels, all of which need to be reviewed," Mr Jennings said.
"No staff member should expect to have to confront this type of appalling behaviour and I think it needs to be treated with utmost seriousness.
"There's also the added dimension beyond that, this is supposed to be a secure government building where classified work is undertaken."
"I would imagine as a result of this, both the Australian embassy in Bangkok and probably embassies worldwide have gone through reviews of their physical security."
The ABC asked DFAT if the Australian government was taking action to assess and improve security at its foreign posts but it did not provide those details.
A DFAT spokesperson said the department was unable to comment further as it was an ongoing legal matter.
"The welfare and privacy of all staff remains a priority for the department and we continue to provide appropriate support," the spokesperson said./-
