The two MPs who appear early on the film are named Mangold and Pennycate. This is an homage to Tom Mangold and John Pennycate, authors of the book THE TUNNELS OF CU CHI, which was an instrumental reference source for the screenplay.
When Beckett and Detective Quan are in the tunnels Beckett is carrying a sidearm in his left hand and rifle with his right hand with the index finger "missing", but in another shot it is carrying the rifle in his left hand and the handgun in his right showing the index finger on the trigger.
After Thomas Beckett has arrived with a Thai Airways plane in Ho Chi Min City he drives with a taxi into town. There are shop signs and ads visible, however in Thai language and not in Vietnamese. (The film was shot in Chiang Mai, Thailand.)
William Avery: [about Beckett]
One way or another, he'll get the job done. His life isn't worth a damn unless he's risking it or taking someone else's.