A group of Thai activists reported to police on Thursday to acknowledge charges brought against them, including charges of illegal assembly, after they staged a demonstration in Bangkok last month to protest a delay to a general election.

Thirty-five out of 39 activists from the Democracy Restoration Group (DRG) reported to police as dozens of reporters waited at Bangkok's Pathum Wan police station.

All 39 have been charged with illegal assembly. Nine face additional charges of breaking a junta order that bans public gatherings and with inciting unrest.

The DRG protest last month on a pedestrian bridge in Bangkok is one of a steady stream of demonstrations that have picked up pace in recent weeks to call for a quick return to democracy.

Some protests have been prompted by a scandal involving the deputy prime minister who is under investigation for failing to declare dozens of luxury watches.

"The activists will acknowledge charges and then they will be taken to the court and it will be up to the court what to do next," a police office at the station told Reuters.

Police said the group would be sent to court and face detention.

"Public protests are a basic right for everyone," activist Netiwit Chotiphatphaisal told reporters before going in to meet with police.

Police did not say whether a police arrest warrant would be issued for the activists who did not show up.

Parliament last month changed an election law, dragging out the time frame for a general election due to take place in November.

The junta has kept a tight lid on dissent since taking power in a 2014 coup. It has banned public gatherings and has ramped up arrests under Thailand's draconian lèse-majesté law.

Activists plan another anti-junta demonstration on Saturday at Bangkok's Democracy Monument.

- Reuters