Is it the one from this web site, credited elsewhere to Albert Collins and also recorded by him:

DON'T YOU GO REACHIN' ACROSS MY PLATE
Word & Music © by Oscar Willis

Now there's just one thing that I just can't stand
And that is sittin' at the table with an ill-mannered man
When he's sittin' on your left before you slip in a bite
He will reach across your plate. Now, I know that's not right.
Now, I like to eat just as well as any man,
But there's some simple rules that even a fool could understand:
Like when you've had one helping, you'd like another piece of cake,
Don't you go reachin' across my plate!

CHORUS: Don't you go reachin' across my plate!
Don't you go reachin' across my plate!
Don't you go reachin'
Don't you go reachin' across my plate!

Now, at dinner last week at my sister Mary's,
Some guy reached across my plate and dipped his coat sleeve in my gravy.
Now, I didn't say a word. I looked him straight in the eye.
He reached across my plate and swiped a big chunk of pie.
Now, I don't care if you do it for a prank,
And I don't care if you need something to drink--
'Specially when I'm out and I'm with my date,
Don't you go reachin' across my plate! CHORUS

Now, at a party last night with all the folks,
You know everyone was there, and it was no joke.
They had barbecued 'possum with rattlesnake gravy,
Chicken fried skunk--you know it smelled real crazy.
Now, everything was fine but one thing had me blue:
Some guy reached across my plate for the armadillo stew.
Now, folks when you're out to dinner, I want you to act real nice.
Say, "Please pass the salsa." "May I please have the rice?"
But just because you happened to come in a little late,
Don't you go reachin' across my plate! CHORUS

Lineation changed a bit to emphasize the rhyme. --JoeClone, 18-Mar-03.