Paetongtarn, 38, is the daughter of Thaksin Shinawatra, the deposed former prime minister who returned to Thailand last August after 15 years in exile. She has only been in office for 10 months and is the country’s second female prime minister, with the first being her aunt Yingluck Shinawatra.
Protesters are calling for the end of Shinawatra leadership.
The rally was organised by the United Force of the Land, a coalition of largely nationalist activists who have protested against other Shinawatra-led governments for over two decades.
In a statement read to crowds, the group said the executive branch and parliament were not working “in the interest of democracy and constitutional monarchy”.
As well as the flags and placards, people carried umbrellas to protect themselves from the rain. When it stopped, a rainbow formed over Victory Monument.