The oblique/objective form is thee (functioning as both accusative and dative), the possessive is thy (adjective) or thine (as an adjective before a vowel—The word "Lord" could not as yet have been used in all the fulness of its meaning As in many cases in the Gospels, it was the natural utterance of respect and awe (John 57;1 I am weak but Thou art strong;
I And Thou Philosopher Martin Buber On The Art Of Relationship And What Makes Us Real To One Another Brain Pickings