It is indeed from one of his plays: The Hostage:

DON'T MUCK ABOUT WITH THE MOON
Brendan Behan

I love my dear Redeemer,
My Creator, too, as well,
And, oh, that filthy Devil
Should stay below in Hell.
I cry to Mr. Khrushchev,
Please grant me this great boon:
Don't muck about, don't muck about,
Don't muck about with the moon.

I am a little Christ-ian,
My feet are white as snow,
And every day, my prayers I say,
For Empire Lamb I go.
I cry unto Macmillan,
That multi-racial coon,
I love him and those above him,
But don't muck about with the moon.
Don't muck about, don't muck about,
Don't muck about with the moon.