The first bomb was found about 6.50am near the fence in front of the OAG by road sweepers of the Bangkok Metropolitan Administration, who notified security guards.
The bomb was connected to a clock and set to explode at 9am.
The other bomb was found in front of the office of the Judiciary Development Institute nearby.
Explosive ordnance disposal police arrived about 8.30am. The two bombs were destroyed.
Nanthasak Poonsuk, the OAG spokesman, said he believed the bombs were meant to be a threat, but did not speculate on the motive.