Wiktionary
they's
contraction (http://en.wikipedia.org/wiki/African%20American%20Vernacular%20English) (contraction of they is English)
Usage examples of "they's".
I spects, if they's to pull every spire o' har out o' my head, it wouldn't do no good, neither,—I's so wicked!
I used to, when I fust begun, have considerable trouble fussin' with 'em and trying to make 'em hold out,—doctorin' on 'em up when they's sick, and givin' on 'em clothes and blankets, and what not, tryin' to keep 'em all sort o' decent and comfortable.
Spects they's gwine to trade ye off with a lot o' cracked tea-pots and sich like!
Speculators buys 'em up cheap, when they's little, and gets 'em raised for market.