Thanarerk Nitiseranee, chairman of the division, said on Sunday that all nine judges made the decision on April 9.
Boonsong and accomplices were charged of malfeasance regarding to government-to-government deals to sell 50,000 tonnes of rice.
The trial will start with defence testimony on June 29.
A source in the division said none of the 21 defendants has yet to file a bail request.
If convicted, they could face life imprisonment. The Attorney General's Office also seeks compensation worth Bt35.3 billion, or half of the deal value.