Police reported loud sound similar to bomb explosions twice at the Chong Nonsi BTS station about 8.50am and closed exits 3 and 4 for safety reasons.
Police also cordoned off the ground near the two exits to examine the cause of the bang.
A Twitter message showed a sheet of glass on the station platform was shattered.
Police also reported loud bangs in Soi 57/1 on Rama 9 road, injuring two city road cleaners at 8.50am, one loud bang outside King Power Mahanakhon Building near the same BTS station at 9am and three bangs near the Government Complex on Chaeng Wattana Road at the same time.
Explosive Ordnance disposal police are at the scene.
In a tweet at 11.12am, Prime Minister Prayut Chan-o-cha condemned those behind the bombing and wrote he had already ordered those responsible to protect the people and take care of affected people in a tweet at 11.12am.