Okeh in a sentence as a noun

Not so; as you can see in my other comment's link, we can cite OK about 90 years before we can cite "okay", and more reliably than that we can cite the alternative spelling "okeh" to 1919, which establishes pretty well that "okay" was not standard then.

Okeh definitions

noun

an endorsement; "they gave us the O.K. to go ahead"

See also: O.K. okay okey