Police suspect a small explosion on Ratchadamneon Klang Road on Wednesday night was from a low-pressure pipe bomb and was aimed at creating chaos.
The police were scheduled to hold an urgent meeting at Chanasongkram Police Station on Thursday morning.
The explosion went off at 8pm inside a garbage bin in front of the old Government Lottery office. Two people who were standing nearby were sent to hospital for treatment.
Suriyaporn Poolsombat, an employee of the Bangkok Metropolitan Administration (BMA), experienced a ringing sound in her ears while Pimwar Raweenoppasit, another BMA worker, had scratches on her arm.
Forensic police officers along with the Explosive Ordnance Disposal team on Thursday morning collected evidence at the bombing scene including metal pieces and electrical circuit panel.