This is not old French, this is Occitan! The traditional band Mont-Jòia (no longer existing) recorded a version of it in 1976 on their album "Cant e musica de Provença, 12th-20th centuries".
The present text was established from the one published in the early 1800's by Damase Arbaud and Rey-Dusseuil in "La confrérie du Saint-Esprit, chronique marseillaise de l'an 1828" in 1829. The song goes back to the 13th century.
In the version above "bòsc" is the standard Oc word but it's actually pronounced "boés" (bwehs). On the 5th line, it's not about standard-non standard, it should be "endormida/endurmia" because it's in the femenine, on the 7th line it should be "m'a" because it's present perfect tense, 11th line it should be "tiratz-vos" it's an imperative form of the verb "tirar" (1st group of conjugation), last line but one it's "me costarà" (vb. costar = to cost). If you listen to their rendition on YouTube you'll hear those words said properly.
There's an English translation on Mont-Jòia's web site that I copy below.

THE LEPER'S DAUGHTER
My father send me to the wood
To the wood to pick olives
My father send me to the wood
To the wood to pick olives
In the wood, pretty wood.

I gathered so many , so many I gathered
That I fell asleep
I gathered so many , so many I gathered
That I fell asleep
In the wood, pretty wood.

I slept so long, I slept so deep
That night fell upon me.
I slept so long, I slept so deep
That night fell upon me.
In the wood, pretty wood.

Along rode a merry Knight
"Let me help you cross the wood"
Along rode a merry Knight
"Let me help you cross the wood"
In the wood, pretty wood.

"Step back, pass you way merry Knight"
You would catch my disease
"Step back, pass you way merry Knight"
You would catch my disease
In the wood, pretty wood.

Leper's daughter I am
Born in the lazaret (lepers place or with lepers)
Leper's daughter I am
Born in the lazaret
In the wood, pretty wood.

Laying my eyes on you
Will cost me my life
Laying my eyes on you
Will cost me my life
In the wood, pretty wood.