No, that’s incorrect.

It’s “Thou are tall” or “Thou art tall”

Nominative   Oblique  Possessive 
Thou         Thee     Thy/Thine* 
I            Me       My/Mine*
He           Him      His
She          Her      Her/Hers**
You          You      Your/Yours**

* Used as an object (It is thine) or historically, when the following word started in the vowel (Thine eyes sparkle like diamonds, Mine ears ache)

** Used as an object (it is hers)

Ahhh, that makes so much more sense.