Merci chef?
As the oil drums have been checked and the lorry is allowed to drive on, the driver says: 'Merci Chef!'.
To most Frenchmen, this means : 'Thank you Head Cook!
Chef means chief or leader, not cook.
shareGrendlkhan is right, it means chief (standing in for 'boss')-
a blokey way the mercenary gives the cops some deference even if its not necessarily sincerely meant.
I gotta find out what makes a man decide not to run, why, all of a sudden, he'd rather die
Yes, essentially he was just saying, "Thanks, boss," relieved that they were letting him through. While they were still checking the drums the mercenary had prepared to use his pistol on them, pumping the slide, in case matters took an unfortunate turn
"Chicken soup - with a *beep* straw."