Hong Sok Hour's request to be released on bail due to ill health is refused.
Activists say local governments are detaining petitioners in their hometowns, meaning that fewer now make it as far as the capital.
A former judge who resigned publicly from the ruling Chinese Communist Party brings his family to the US.
But nationalist actions, such as boycotts, are not the answer to a growing deficit, he says.
The group of nine says they fear persecution if returned to Cambodia's communist neighbor.
A diplomatic source says Lao-born expat did not have access to legal assistance.
They want government leaders to seek a rate lower than three percent on the U.S. $500 million loan.
Police say they aren't treating the explosions as an act of terrorism.