These are all old English words, no one would use them anymore except for some writers of historical novels. They would be understood if you used them however. But you would be regarded as very unusual. Thee - someone is referring to you. Thy - something belonging to you - thy hat Thine - being part of you - thine eyes.

For example: When a man and woman get married, the man (as he is putting the wedding ring on her finger) might say, "With this ring, I THEE wed." (= When I put this ring on your finger, I am marrying YOU.)