A Boeing 767-300 operated by Saudi Arabian Airlines was damaged in a landing accident at Madinah-Mohammad Bin Abdulaziz Airport (MED), Saudi Arabia. When preparing for landing in MED, the flight crew lowered the landing gear but the right main landing gear did not lower into the extended position. The flight crew notified the MED Air Traffic Control Tower of the discrepancy. The flight crew attempted to use the alternate procedure to lower the right main landing gear without success. The flight crew eventually landed the aircraft with the right main landing gear in the retracted position. The aircraft made a smooth touch down, slowing until the right engine nacelle contacted the runway. The aircraft remained under control during the landing with no injuries to the aircraft occupants. During the evacuation of the aircraft, fourteen passengers received minor injuries and three passengers were seriously injured while sliding down the L-1 slide. Findings 1. A foreign air carrier, the C-11 maintenance check provider, did not identify the number 1 or number 7 brake assemblies having eroded safety wire holes in the lock bolts installed on the brake rod retaining pin when performing a C-11 maintenance check. 2. All lock bolts installed on the brake rod retaining bolts should have been identified and evaluated for serviceability and replaced as necessary. 3. Orient Thai did not identify eroded safety wire holes in the lock bolts during the performance of maintenance activities including, brake replacement tasks, daily checks, and transit checks. 4. The accident was precipitated by the loss of two lock bolts that were not (or were not able to be) safety wired in place. Safety wiring the lock bolts would have prevented the right main landing gear brake rod retaining bolt from loosening and falling away from the pin.