The attack occurred as the protesters were forming their procession at Banthad Thong Road, waiting for their leader Suthep Thaugsuban to join and lead them to the next destination. Mr Suthep was not hurt in the incident.
The Bangkok Metropolitan Administration's Erawan Emergency Medical Centre reports that at least 36 people were injured in the explosion and they were rushed to nearby hospitals.
The demonstrators were asked to leave the area immediately for their safety, while protest movement guards searched for suspects claimed to have been seen in an abandoned building where they also collected some possible forensic evidence.
Police then arrived amid some disgruntled protesters. They said the PDRC guards are allowed to inspect the scene until they are satisfied. A combined forces of police explosive ordnance disposal team, soldiers and municipal officials then searched the deserted building and found parts of two M16 assault rifles, two knives, four walkie-talkies and personal items. All were collected for examination and further investigation as to whether they were related to the bomb attack
At least eight people have been killed and several hundred have been injured since the series of anti-government protests started in November.