An Il-76 cargo plane carrying 35 tons of weaponry was seized during refueling at Bangkok's Don Muang airport on December 12.
The plane's five crew members, of whom one is from Belarus and the other four are from Kazakhstan, were arrested following the seizure and taken to Bangkok's Klong Prem Central Prison.
The crew may be charged with illegal storage and transportation of weapons and providing false information.
The crew members have said they were unaware of the military nature of the cargo. They say they were told the cargo was oil drilling equipment.
The latest U.N. sanctions, which ban the transport of certain weapons from or to North Korea, were imposed in June after the reclusive communist regime conducted a nuclear test and test-fired missiles.
The sanctions were aimed at derailing North Korea's nuclear weapons program, but also banned the North's sale of any conventional arms.