I searched for some time to find the lyrics to this song. And never did. Finally transcribed it myself. Had the hardest time because one single bit utterly flummoxed me. I could not make out what was being said, and assumed it was a language thing. I thought it was Spanish. Once I wrote out what I was phonetically hearing, it was obvious. Three syllables, accent on the last (which is what probably threw me). "ma", like your mom. "ri", like the first part of reed, without the "d". "ah", as in, "say ah".

Without further ado, as performed on Barton, Para, Paton - Twas On a Night Like This (Folk Legacy). I have no idea what the source is.

Chocolate Burro

In Bethlehem town, all merry and gay
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
The chocolate burro comes today
With boxes and bars for all who will pay
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
He jingles his bells to not delay

Ma-ri-a, Ma-ri-a, come a runnin' I say
There's chocolate sweet for your baby today
Ma-ri-a, Ma-ri-a, come a runnin' I say
There's chocolate sweet for your baby today

When Mary the maid was sewing that day,
   When she heard a …
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
A'patching Saint Joseph's coat of gray
She didn't look up, her eyes did not stray
To the …
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
She knew that for sweets she could not pay

Ma-ri-a, Ma-ri-a, come a runnin' I say
For the chocolate one will be going away
Ma-ri-a, Ma-ri-a, come a runnin' I say
For the chocolate one will be going away

Then into the bay with a burst and a bray
   And a …
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
The chocolate burro makes his way
Right up to the crib with all his display
   And a …
Ring-a-ling, a-ling-a-ling, ring-ling-a-ling, a-ling-a-lay
He kneels with the other beasts to pray

Ma-ri-a, Ma-ri-a, come a runnin' I say
There's chocolate sweet for your baby today
Ma-ri-a, Ma-ri-a, come a runnin' I say
There's chocolate sweet for your baby today