I Thank THEE, for THOU guided me to the straight pass or I thank THEE for THOU guided me to the straight pass. Should I put a comma before for?
"For" in this sentence is synonymous with "because," so we can follow the same comma rules that we do with because.
The article above states that you almost never use a comma before because. The only exception is when you need the comma to make the sentence meaning clear (e.g. "He didn't run because he was afraid" vs. "He didn't run, because he was afraid").
In your case, there is not ambiguity in what your sentence means, so you don't need a comma (at least according to modern usage rules).