Protesters led by former opposition politician Suthep Thaugsuban started blocking major intersections late on Sunday, aiming to create traffic chaos in a city of an estimated 12 million people where roads are clogged at the best of times.
The upheaval is the latest chapter in an eight-year conflict pitting Bangkok's middle class and royalist establishment against the mostly poorer, rural supporters of Yingluck and her self-exiled brother, former premier Thaksin Shinawatra.
Thaksin was ousted by the military in 2006 and sentenced to jail in absentia for abuse of power in 2008, but he still looms large over Thai politics and is the dominant force behind his sister's administration from his home in Dubai.
Eight people, including two police officers, have been killed and scores wounded in violence between protesters, police and government supporters in recent weeks, although there has been no sustained fighting between rival groups.
Red-shirted supporters of Thaksin started rallies in several regions on Sunday but steered clear of Bangkok.
One person was killed in a shooting overnight near a planned protest site in northern Bangkok. "An unidentified gunman shot a man near a roadblock set up by anti-government protesters. It is unclear at this point if the man was a protester or not," police spokesman Piya Utayo said.
Yingluck has called a snap election for February 2, which protest leader Suthep has rejected.
"The people cannot negotiate ... there is no win-win situation, there is only win," he said in a speech to demonstrators at Bangkok's Democracy Monument on Sunday.
Earlier, however, he said he would stand down his movement if, as some fear, violence escalates into a civil war. "If it becomes a civil war, I will give up. People's life is precious for me," he said, according to the Sunday Nation newspaper.
Suthep's stated goal is to eradicate the influence of the Shinawatra family on Thai politics.
