Still haven't seen the exact version I learned...

Did you ever stop to think when a hearse goes by
that you might be the next to die?
They wrap you in a long white sheet
and bury in the ground 6 ft. deep.
All goes well for about a week,
and then your coffin begins to leak.
(I think there's a line missing that goes here)
The worms crawl in and the worms crawl out,
and the worms play ping-pong across your snout.
Then your stomach turns to slimy green
and pus runs out like slow whipped cream.
Then you sop it up with moldy bread
'cause that's what you eat when you are dead!