Investigators of Chana Songkhram and Nang Lerng police stations yesterday applied via video conference to the Criminal Court for approval to detain the 16 suspects for a further 12 days, from March 22-April 2.
Investigators said they still had to question 11 more witnesses and awaited the results of medical examinations of police and some witnesses who were injured during the protest.
The police opposed bail, arguing that the suspects could repeat the alleged offences, causing disturbance and damage to public property.
According to police, the 16 were among about 500 people who gathered on one side of the Supreme Court on March 20, using loudspeakers to criticise the government.
The crowd later moved to Ratchadamnoen avenue and spraypainted shipping containers stacked up by police to block their passage, and pulled them down with ropes. Protesters also threw firecrackers and glass and iron projectiles at police, using slingshots, and damaged police traffic kiosks, vans and other property.
Poilce retaliated, using water cannon against them.
The protesters had broken the law prohibiting the gathering of 10 or more people to cause disturbance. They defied police orders to disperse and instead obstructed police performing their duty, police allege.
The suspects have denied the charges.
After cross-examination, the court allowed the suspects to be freed on bail, with a surety of B35,000 each.