Bangkok: A Cambodian court has quashed a bid by Australian filmmaker James Ricketson to have espionage charges against him dismissed.

Mr Ricketson was sent back to Pray Sar, a notoriously harsh and overcrowded prison on the outskirts of Phnom Penh on Thursday, where he has contracted a skin disease.

In this photo from Cambodian website Fresh News, Australian filmmaker James Ricketson is seen apparently operating a drone.

His lawyer Ou Helene told the Phnom Penh Post that a closed court hearing rejected a request to annul the proceedings and dismiss a charge of gathering sensitive information with the intention of supplying it to a foreign state.

"The decision is final…the decision to dismiss the annulment request cannot be appealed," she said.