Thai National police chief Pol General Kowit Vatana signed on Monday an endorsement recommending four military officers be charged with trying to assassinate ousted prime minister Thaksin Shinawatra in August, Thai media reported.

Kowit's signature, which is the final step in indicting the senior military officers, came after a one hour meeting with several senior police officers including chief investigator of the case, Central Investigation Bureau head Pol Lt General Montree Jamroon, said the report from news network The Nation.

The four suspects are Maj-General Phairoj Theerapharb, Colonel Suraphol Supradit, Lt-Colonel Manas Sukprasert and Lieutenant Thawatchai Klin-chana, all of whom are attached to the Internal Security Operations Command (ISOC).

The officers all face six charges: criminal conspiracy to commit premeditated murder; attempting to kill a state official on duty; possessing explosives; having non-authorized items in their possession; forging and using official documents; and criminal conspiracy.