The CRD had earlier vowed to lay siege to the NACC office if it failed to look into its complaint that six NACC members had carried out their duty without having been royally endorsed.
Authorities deployed two companies of anti-riot police to keep the peace, fearing clashes involving the PDRC group, who had been camping at the NACC as a show of support.
After half an hour of verbal attack, the CRD advanced towards the PDRC, who retreated.
After the PDRC left, CRD set up tents to stage a sit-in protest at the NACC office.
The CRD guards meanwhile detained Chokchai Uthaichan, 58, a retired Navy sailor, who drove his pick-up truck into the barricades set up by the CRD. He said he sold goods to PDRC protesters and did not know the area had been taken over by the CRD.
A monk identified as Prat Supawirut escaped being assaulted by CRD protesters by fleeing into a shop nearby after one shouted he was a PDRC protester.