It's stoker.

It sounds better than stroker.

And the lyricist, whoever it was, couldn't have cared less about 2-strokes, 4-strokes, or risqué double-entendres, for that matter. He was just trying to get the meter and feel right, the way Chuck Berry used to do: "Ridin' along in my calaboose." "We parked way out on the Kokomo." Nobody had ever used those words for "car" or "moonlit beach", but we knew exactly what they meant.

BTW, I would guess that Hank did not write the tune. Many of the commercial, novelty (cutesy) tunes were written for him.