Three people have been killed and 52 injured in a bomb attack in Bangkok and a shooting in eastern Thailand.
In eastern Thailand, a five-year-old girl was killed and 30 other people were injured after gunmen sprayed bullets on an anti-government rally in eastern Thailand.
Gunmen on two pick-up trucks opened fire on a packed market place.
The incident happened in Khao Saming district of Trat province where an anti-government rally was taking place, according to police lieutenant Thanaphum Naewanit.
Television footage showed dozens of upturned plastic chairs at the rally site and abandoned street stalls after people fled the shooting in panic.
Meanwhile, a bomb killed two people and injured at least 22 in a busy shopping district of the Thai capital.
It exploded hours after supporters of Thai Prime Minister Yingluck Shinawatra promised to get tough with demonstrators paralysing parts of the city.
But it was not immediately clear who was responsible.
The bomb exploded near one of the few large protest sites remaining.
It left a trail of blood and sandals on the streets of the popular Rachaprasong shopping area, much of it in front of a store selling tee-shirts emblazoned "Land of Smile".
Three children suffered serious head injuries, Erawan Medical Center, which monitors hospitals, said. One died.
Fears of widespread violence have intensified in step with ongoing protests to topple Prime Minister Yingluck Shinawatra, with tensions soaring on both sides of Thailand's political divide.
Most of the violence has taken place in or around Bangkok, where protesters are carrying out a self-styled "shutdown" of several key intersections across the city centre.
Ms Yingluck is under intense pressure from various legal challenges as well as the street protests demanding her resignation.
She faces charges of neglect of duty over a controversial rice subsidy scheme that could see her removed from office.
Protesters accuse Yingluck's billionaire family of using taxpayers' money to buy the loyalty of rural voters through populist policies such as the rice scheme.
They are demanding she steps down to make way for a temporary unelected council that would oversee loosely defined reforms to tackle corruption and alleged vote-buying.
Her government was last week also banned from using force against peaceful demonstrators by a court ruling which government officials said crippled their powers to handle the mounting violence.
Thailand has been scored by deep political divisions since a military coup in 2006 ousted then-premier Thaksin Shinawatra - Yingluck's older brother.