An Indonesian woman has been sentenced to six months in jail after she documented sexual harassment by her employer, sparking condemnation from rights groups on Thursday.

Baiq Nuril Maknun, 37, recorded a telephone conversation with the head teacher of the school where she worked on the Indonesian island of Lombok, who she accused of making repeated unwanted sexual advances, her lawyer Joko Jumadi said.

Indonesia's top court convicted her of recording and spreading "indecent" material under the country's electronic information and transactions law after a colleague used the audio to lodge an official complaint against the head teacher.

"The Supreme Court judges were satisfied that she has violated the law," court spokesman Suhadi, who like many Indonesians uses only one name, told the Thomson Reuters Foundation by phone from the capital Jakarta on Thursday.

The court sentenced her to six months in prison and fined her 500 million rupiah (R488 464.64) after overturning a 2017 acquittal from a lower court, said Suhadi.

Campaigners called the ruling a "travesty".

"It appears a woman was criminalised simply for taking steps to redress the abuse she experienced," Amnesty International's Indonesia executive director Usman Hamid said in a statement.

"It is a travesty that while the victim of the alleged abuse has been convicted ... little if any action appears to have been taken by the authorities to investigate what appear to be credible claims."

Maidina Rahmawati from the Institute for Criminal Justice Reform, a Jakarta-based non-profit, said the ruling could be used to deter other victims from reporting future abuses.

"This case is just an example of how the law, which is too vague, could be used against vulnerable women who were trying to protect themselves," she said by phone.

One third of Indonesian women have faced physical or sexual violence, according to a government survey released last year, prompting call from campaigners for action.

The latest court ruling was delivered in a closed-door deliberation on September 26 and only made public this week.

Maknun's lawyer Jumadi said the mother of three would file a judicial review to challenge the court's ruling, but could be detained by authorities at any time.

"She is a victim and she just wants justice," said the lawyer.