Thai riot police on Saturday fired water cannon, tear gas and rubber bullets to repel a crowd of several hundred young anti-government protesters.
The demonstrators threw rocks, bottles, fireworks and fired slingshots as the clash, in the Din Daeng area of Bangkok, descended into an hours-long confrontation, often obscured by swirling smoke.
Video pictures showed several people being treated for apparent injuries at the scene, including at least one policeman.
The march was called off in the early evening but disturbances continued, with many of the crowd continuing to bate the police and hurl objects.
The protesters, led by the Free Youth group, are demanding Prime Minister Prayuth Chan-ocha's resignation over his handling of the coronavirus crisis which has seen the number of confirmed cases spiralling and the healthcare system stretched to the limit.
Thailand reported a new high of 21,838 new cases on Saturday, with 212 more deaths.
They are also calling for part of the budget for the monarchy and the military to be redirected into the COVID-19 fight.