"good, proper, excellent," 1934, jazz slang, from American English dialectal pronunciation of right (adj.).
Online Etymology Dictionary, © 2010 Douglas Harper
Examples from the Web for reet
"Bessie, you're reet clipt and heeled for sure," responded her companion.
"I mak' no doubt as you're reet, Dick," said Matthew, meekly.
Now, if 'night' is 'nicht,' why is 'right' 'reet'—either 'the noo' or at any other time?The History of "Punch"
M. H. Spielmann
I ha' na getten no reet to no soart o' pleasure, I dare say.
What mowtn't be reet fur other lasses to do, is reet enow fur me.