A bomb exploded next to the Army Survey Department's fence off Rajdamnoen Avenue Sunday night, causing injuries to two ordnance disposal officers at the scene.
The explosives was in a black cardboard box placed at a phone booth in front of a small soi between the Army headquarters and the Army's Survey Department.
The box was spotted by bystanders at the Rajdamneon Boxing Stadium across the Army headquarters and after the explosion, another box was found 50 metres away from the first one.
After being informed, the bomb disposal unit rushed to the scene at around 9pm. But while inspecting the box, the bomb went off.
The explosion seriously damaged the right wrist of a bomb disposal officer and injured another in the chest but not seriously. Both were sent to Hua-Chew hospital.
The site has not yet been sealed off, just barricades erected around it.
Sniffer dogs have been used to detect more bombs at the scene and nearby areas.
So far, there is no initial comment available from police and the army about the motive of the explosion.

Quelle Bangkok Post