The line is:
"They think you're an O.A.S. spy,
gonna shoot them as they walk by"
It refers to an Algerian seperatist group that was active in France in the early sixties. Bert would have been hitching about at this time.
In a live performance ('Live at the 12 Bar'), he sings
"Strollin' down the highway
I'm gonna get there my way
Dusk 'till dawn I'm walkin'
the guitar on my back is rockin"
"People think I'm crazy
Lord above, I ain't lazy
Sunshines all day long
and the garlic is far too strong"
"The cars won't stop for no one
They think you're just a rollin' bum
They think you're an O.A.S. spy
Gonna shot them as they walk by"
HTML line breaks added --JoeClone, 30-Nov-01.