The bomb near garbage bins on Ratchadamnoen Road that slightly hurt two women on Wednesday night was a low-impact improvised pipe bomb, according to police.
Bangkok police chief Pol Lt Gen Sanit Mahataworn said on Thursday police were checking the closed-circuit camera footage in front of the old Government Lottery Office building to identify the suspects.
"I personally would not go as far as saying it was politically motivated but we can't rule out anything until we find the perpetrators," he said.
According to earlier reports, police found pieces a 0.5-inch-by-four-inch PVC pipe, explosive powder and a timer in the area.
Police believe it is a pipe bomb normally used to create unrest with no intent to kill or damage assets.
They said it is like the bomb found in a phone booth at Major Ratchoyothin in 2007. The circuit board has been sent to determine whether they are of the same type.