Kim posted a photo of Psalm West Monday morning ... the first one since his birth. She captioned the pic, "Psalm Ye" ... so guess we know what his nickname is gonna be. And, yes ... it's only a nickname. We've seen his birth certificate, and it doesn't list a middle name.

Anyway, back to Psalm's adorable mug. He's looking pretty chill in a onesie for his big public debut. We know what you're thinking, and yeah ... the Kardashian is strong with this one.

As we reported ... Kim and Kanye welcomed Psalm -- their fourth child together -- last month via surrogate. He arrived at 6 lbs and 9 oz., and was delivered by go-to Kardashian doctor, Dr. Paul Crane.

Welcome to the show, Psalm! We know he's already got a manager/grandma ... if he wants one.