On top of a giant yellow inflatable duck, a rebel Buddhist monk in saffron robes displayed a defiant three finger salute at a pro-democracy protest in central Bangkok.

Scores of the pool toys bobbed through a crowd some 20,000 strong yesterday as activists descended on the Thai national police headquarters to throw paint and scrawl obscene anti-royal slogans on the streets.

The cute yellow birds are fast becoming a symbol of the Thai protests after demonstrators used them a day earlier as shields against the burning spray of police water cannon and tear gas at a rally near parliament.

Tuesday saw the most violent confrontations since the rallies kicked off in July - six people were shot during scuffles between royalists and democracy activists.

The youth-led movement is demanding a new constitution, making unprecedented calls to reform the untouchable monarchy, and for the resignation of Prime Minister Prayut Chan-o-cha, who came to power in a 2014 coup.

Footage of Thailand's so-called "rubber duck revolution" has gone viral on social media this week.

"If the politics are good, ducks will only be used in the pool," one Twitter user remarked.

"Here you go, the most terrifying weapon from the protesters' side: an inflatable duck," a Facebook user wrote.

"Duck is a fighter, no matter how much people bully him, he still keeps smiling," a Thai man tweeted alongside a picture of a battered and slightly deflated duck.

The duck protest appearances have also inspired a bevy of artwork.

Thai artist Wannasin "Matthew" Inpin used a tablet computer to whip up a cartoon of a part-duck part-strong man figure protecting protesters.

"Rubber ducks are very fragile and I think it is not a fair fight at all but I think this act shows the protesters' fearlessness and strength to fight back," he told AFP.

"That's why I drew the duck as a strong animal who protects protesters and is not afraid of dictatorship."

The inflatable pool ducks are retailing on Lazada Thailand, an online shopping portal, for 499 baht (€14).