As dozens of police watched, the protesters sang a parody of the theme song for Hamtaro -- a popular Japanese anime character that is a sparkly-eyed hamster -- replacing the lyrics with the refrain "dissolve the parliament".
The demonstrators brought a different mood from a week ago, when thousands of young, black-clad Thais shouted vitriolic anti-government rap songs at the monument.
But the message remains the same, as boom-box wielding Thais started to jog around the monument in an apparent symbolic attempt to show how the kingdom's politics falls into a cycle they wish to break.
"I want a future where people can fight for democracy," said Bowie, a 27-year-old lawyer who only provided his nickname.
"We need freedom to fight because this government attacks everyone that is not on their side," he said before running to join his fellow protesters.
The kingdom's rambunctious political scene has long been defined by coups and deadly street protests.
The current government headed by former army general-turned-premier Prayut Chan-O-Cha is regarded as part of the pro-military royalist establishment.
But a freefalling economy due to the coronavirus epidemic, and the recent disappearance of a pro-democracy activist has stoked the anger of younger internet-savvy Thais who are well-versed in viral movements.
The Hamtaro theme was chosen for its viral potential in other countries, said Jessie, a 19-year-old university student.
Most notably, the jaunty chorus -- "The most delicious thing is sunflower seeds" -- have been changed to "The most delicious thing is the people's taxes".
"They should use our taxes to develop our country," Jessie said.
"We are scared but for us, it is important to start speaking up about it," she told AFP. "We need change right now."
Sunday's gathering was the latest in a string of rallies across the country, displaying a deep well of discontent among young Thais from all walks of life.
The day before, LGBT activists gathered at Democracy Monument to call for marriage equality and demand for Prayut's resignation.
The premier said last week he was "worried" for the parents of the young protesters, and defended keeping the emergency laws in place -- which critics say is a way to erode freedoms.
The kingdom's powerful army chief, General Apirat Kongsompong, called on Friday for all Thais to keep their minds "neutral", especially on social media.
"Although I am the army chief, I speak as a Thai citizen that whatever you do, you will regret it when looking back," he said.