Myanmar’s ousted civilian leader, Daw Aung San Suu Kyi, was convicted Monday and sentenced to four years in prison for possessing walkie-talkies in her home and for violating Covid-19 protocols.

Altogether, Ms. Aung San Suu Kyi, 76, has been sentenced to a total of six years in prison so far, with many more charges pending against her.

Monday’s guilty verdict on three counts comes on top of her Dec. 5 conviction on charges of inciting public unrest and a separate count of breaching Covid-19 protocols. Initially sentenced to four years on those charges, that sentence was cut in half by the army commander in chief, Senior Gen. Min Aung Hlaing, the leader of the Feb. 1 coup that forced her from office.

As the first anniversary of the coup approaches, the court found Ms. Aung San Suu Kyi guilty of violating Myanmar’s import-export law and its telecommunications law by possessing the communication devices. Her defenders have said the walkie-talkies belonged to her security detail, and that the charges were bogus and politically motivated.

She was sentenced to two years on the Covid protocol, two years on the charge of importing the walkie-talkies, and to one year for violating the telecommunications law. The sentences connected to the walkie-talkie charges are to run concurrently.

Ms. Aung San Suu Kyi has been held incommunicado in a house in Naypyidaw, the capital of Myanmar. Amnesty International called the walkie-talkie charges trumped up, saying “they suggest the military is desperate for a pretext to embark on a witch-hunt and intimidate anyone who challenges them.”

The charge of importing the devices — the first of many charges brought against her — was filed on Feb. 3, two days after the coup, and the court proceedings have lasted nearly a year.

The guilty verdict for violating Covid protocols stemmed from an episode during the 2020 election campaign in which she stood outside, in a face mask and face shield, with her dog, Taichito, at her side, and waved to supporters passing by in vehicles. The same incident was the basis of her conviction on a nearly identical charge in December.

Ms. Aung San Suu Kyi faces at least seven more charges — including five counts of corruption — with a potential maximum sentence of 89 years if she were to be found guilty on all remaining charges.

Human Rights Watch said the military regime was making itself appear ridiculous by accumulating convictions on flimsy, politically motivated charges.

“The Myanmar junta’s courtroom circus of secret proceedings on bogus charges is all about steadily piling up more convictions against Aung San Suu Kyi so that she will remain in prison indefinitely,” said Phil Robertson, the group’s deputy Asia director.

Ms. Aung San Suu Kyi was the Nobel Peace Laureate in 1991 and led her party, the National League for Democracy, to landslide victories three times between 1990 and 2020, but the military allowed her to form a government only once, in 2016.

She spent a total of 15 years under house arrest between 1989 and 2010. She later damaged her reputation as an international icon of democracy by not speaking out against the military’s brutal ethnic cleansing of Rohingya Muslims, which drove more than 700,000 Rohingya into Bangladesh.

Since the coup, Ms. Aung San Suu Kyi and the ousted president, U Win Myint, have been held under house arrest in undisclosed locations near the capital, Naypyidaw. Mr. Win Myint was also convicted on Dec. 5 of violating Covid-19 protocols and sentenced to four years. The coup leader also cut his sentence in half.

Ms. Aung San Suu Kyi’s trials are being held in a house in Naypyidaw that was converted into a courtroom. No members of the public are allowed to attend, and her lawyers are forbidden from speaking about the case.

On Dec. 30, a police court sentenced Daw Cherry Htet, 30, a police lieutenant and former bodyguard to Ms. Aung San Suu Kyi, to three years in prison for violating rules on police conduct by posting messages on Facebook that the court deemed inflammatory.

In one post, she said simply, “We miss you Amay,” using the Burmese word for mother. The former bodyguard was also accused of communicating with the National Unity Government, the shadow government formed after the coup by ousted elected officials and other opponents of the military.

Monday’s conviction of Ms. Aung San Suu Kyi came as the military continued its effort to suppress pro-democracy protests, combat a budding resistance movement and battle ethnic groups seeking autonomy. Soldiers and the police have killed at least 1,447 civilians since the coup and detained nearly 8,500, according to the Assistance Association for Political Prisoners, a rights group.

The Tatmadaw, as the Myanmar military is known, was accused of committing one of its largest massacres on Christmas Eve when soldiers killed at least 35 fleeing villagers and burned their bodies. Save the Children, one of the groups that condemned the massacre, said two of its staff members were among those killed as they returned home for the Christmas holiday.

Sui-Lee Wee contributed reporting.