The death toll from a blast in Bangkok rose to three on Monday.
On Sunday, an apparent grenade blast near an anti-government protest site killed a woman and a four-year-old boy.
Doctors said on Monday that the little boy’s sister died later of brain injuries.
Twenty-two people were hurt in Sunday’s blast, including a nine-year-old boy who is in intensive care.
Sunday’s attack came hours after gunmen opened fire on an anti-government rally in eastern Thailand, killing a five-year-old girl.
Thai PM Yingluck Shinawatra has condemned the attacks, describing them as “terrorist acts for political gain”.
UN Secretary Ban Ki-moon has also spoken out, calling for violence “from any quarter” to end immediately.
Meanwhile, the Thai army chief says the military will not intervene with force in the country’s crisis.
Thailand’s political crisis has become increasingly violent since mass protests began in November.
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