The PDRC demonstrators started to move out from Lumpini Park at 9.30am.
According to the plan, they are to march along Rama IV road to Hua Lampong railway station, turn left to Surawong road and make another left turn along Mahesak road before returning to Lumpini. The total distance is 5.8 kilometres.
About 2,000 PDRC guards are reported to be deployed along the route to provide security for the marchers. Police have also been asked to help facilitate traffic flow.
The protesters were being greeted and cheered by people along the march route.