Lawyer Sirichai Pakdee failed in bid to have the Bangkok Military Court take custody of Lieutenant Thawatchai Klinchana.

Thawatchai's lawyers submitted the request earlier in the day.

It was not clear why the military court rejected the request. One of Thawatchai's lawyers, Nitikorn Nontasawas, said he would consult his client's family before deciding whether to appeal.

Crime Suppression Division (CSD) chief Maj-General Winai Thongsong said police had no objection to Thawatchai being transferred to the military court's custody.

"We will only object his bail request," Winai said.

Thawatchai - an officer at the Internal Security Operations Command (Isoc) - has been in police custody since August 24, when he was arrested in a bomb-laden car near caretaker Prime Minister Thaksin Shinawatra's residence.

Police have treated the case as a foiled assassination plot against the premier. Thawatchai has maintained his innocence, saying a friend asked him to fetch the car and he had not known it contained bombs.

Speaking before the military court's decision, another of the Thawatchai's lawyers, Sirichai Pakdee, said his client had invoked his right to testify only in court and thus police did not need to keep him in custody any longer.

"The suspect should be transferred to the custody of the military court," he said.

Sirichai accused the police of violating Thawatchai's rights by releasing a video recording of him making a confusing confession on Monday.

Nitikorn said police did not summon his team to the interrogation despite the law requiring the suspect's lawyer to be the present.

"The lawyer in the video recording was not appointed by Thawatchai," Nitikorn said.

He dismissed a police claim that they appointed a lawyer for Thawatchai in good faith because he had no lawyer at the time.

Nitikorn insisted Thawatchai had appointed him as his lawyer before the interrogation.

He denied that he and other lawyers for Thawatchai were close to General Pallop Pinmanee, who was sacked as Isoc deputy director following Thawatchai's arrest.

Meanwhile, CSD chief Winai instructed investigators into the alleged assassination plot to be careful when speaking to the media.

However, a police source disclosed that a signal-receiving circuit found in the bomb-laden car had been sent to King Mongkut's Institute of Technology Ladkrabang to test whether it was functional. Also, many fingerprints were found on the black tape binding the TNT explosives found in the car.

"We are trying to match the fingerprints to those in our database," the source said.