A small explosion slightly hurt a Bangkok Metropolitan Administration worker on Sukhumvit Soi 40 on Friday afternoon.
Thong Lor police were reported about the blast at 1pm.
While the woman was sweeping the pavement in front of Unesco's Bangkok office, she picked up a cloth bag hidden in a shrub and kept it with her. While she continued to clean the area, the bag fell so she opened it. It suddenly exploded and hurt her right leg, according to Thai media reports.
Police initially assumed it might have been left there by some youths as the area is close to a school
She was sent to Chulalongkorn Memorial Hospital. EOD police are checking the type of the explosive.
Police later said the ping-pong bomb was among weapons including about 10 big knives stashed by vocational students for use in brawls.
Video by Pattarapong Chatpattarasill