Suu Kyi, a Nobel laureate, has already received at least 23 years in prison in various instances, most of which involved allegations of corruption.
A court in military-run Myanmar has sentenced former leader Aung San Suu Kyi and her senior economic adviser, Australian Sean Turnell, to three years in prison.
They were sentenced on Thursday for breaking secret legislation, according to a source familiar with the proceedings.
The duo had pleaded not guilty to charges of breaking the official secrets act, which carries a potential 14-year penalty.
"Three years each, no hard labour," a source who declined to be identified due to the sensitivity of the issue told Reuters.
Thousands of people, including politicians, MPs, bureaucrats, students, and journalists, have been detained since the military ousted Suu Kyi's democratic government in a coup at the beginning of last year, along with Turnell, Suu Kyi, and other members of her economic team.
Turnell is also accused of violating immigration laws, and if found guilty, he may spend up to five years in jail. According to a second source and media sources, the court is anticipated to make a decision on that matter on Thursday.
Suu Kyi, a Nobel laureate, has already received at least 23 years in prison in various instances, most of which involved allegations of corruption.
All allegations made against her have been refuted.
The charges against Suu Kyi, according to the military's detractors, are intended to prevent her from ever engaging in politics again and to undermine the military's hold on power.
On Thursday, attempts to reach a junta representative for comment were unsuccessful. The junta maintains that Myanmar's courts are impartial and that individuals who have been arrested are being treated fairly.
Turnell, who teaches economics at Macquarie University in Australia and is also a detainee, has been held captive for a few days following the coup.
His wife, Ha Vu, who is based in Australia, said she and her family were "heartbroken" at the verdict and called for him to be deported.
"Sean has been one of Myanmar's greatest supporters for over 20 years and has worked tirelessly to strengthen Myanmar's economy. Please consider the contributions ... and deport him now," she said in a Facebook post.
"The Australian government has consistently rejected the charges against Professor Turnell. (It) rejects today's court ruling ... and calls for his immediate release," Foreign Minister Penny Wong said in a statement.
Australian consular officials tasked with assisting Turnell were denied access to the court, Wong said.
Thursday's sentencing took place in a closed court in the capital, Naypyitaw. The defendants' exact offence under the official secrets act remains unclear, though a source previously said Turnell's offence "relates to an allegation that he had government documents".
An analyst for the International Crisis Group think tank, Richard Horsey, called the proceedings "a show trial".
"For Sean the hope now must be that - having already been in detention for almost 20 months - he will be released soon from this terrible ordeal and reunited with his family," he said.