The bomb exploded at around 2.15am this morning at the tow truck belonging to Dusit police station which parked near Parusakawan Palace, opposite the 1st Army Region headquarters on Rajdamnoen Nok Avenue.
The Explosive Ordnance Disposal (EOD) unit said after inspecting the scene that the explosive device was a homemade bomb, using C-4 explosive weighing some 500 grammes.
It was placed on the car by unknown assailants before leaving the scene.
The blast caused a 10 cm deep and a 30 cm wide hole at the footpath. The truck's tyre was damaged, and some lights and windows at the palace were shattered.
Police were checking CCTV footages to gather evidence that could lead to the arrest of the bombers.