Paramjeet Kaur, 41, who claimed she was a "sovereign" when told to put on her mask in Shunfu Mart, has pleaded guilty on Friday, May 7.
In total, she faced seven charges: Four for breaching Covid-19 regulations and three others for public nuisance, for failing to report her change of home address and for refusing to sign her statement at a police station.
She was convicted of one count each of breaching Covid-19 regulations and for public nuisance.
The remaining charges will be taken into consideration during her sentencing.
Kaur was arrested on May 4, 2020, and was charged on May 5.
Kaur was caught on video in May 2020 claiming that she was a "sovereign".
This was after she was told to wear a mask but ended up in a quarrel with passers-by at Shunfu Mart near Upper Thomson Road.
She was heard saying: "It means I have nothing to do with the police, it means I have no contract with the police. They have no say over me."
A man off-camera can be heard sayings: "This doesn't even make any sense. If you're a person in Singapore, you have to follow the rules of Singapore."
The incident drew widespread criticism and ridicule among the public in Singapore.
Law and Home Affairs Minister K. Shanmugam stepped in to comment on the incident and wrote in a Facebook post that he had "checked up" what "sovereign" meant.
He said: "There is a movement in the United States, and adherents to that movement, (broadly speaking) reject government, reject the police and any kind of authority... Such people should not live within society - she should not expect any of the benefits that come from this system of governance, including her security, medical care, other benefits."
For failing to wear a mask over the nose and mouth, a first-time offender can be jailed for up to six months, or fined up to S$10,000, or both.
Repeat offenders can be jailed for up to a year, or fined up to S$20,000, or both.