Why has the second person, singular disappeared from the english language? The only place you see: thou, thee, thine, etc. used is in prayers, hymns, and Shakespeare.
It has just changed to a more modern usage, but is still very much present. YOU used it yourself in your question!
Second person singular is also 'you', the same as second person plural.
Thee, Thine, thou are considered very old fashioned. They are used in many hymns because they were written long ago, it is also a sign of respect to a higher authority, There is no distinction between you (sing) and you (pl),
The use in the bible depends on which version or translation you use. Modern bibles drop the formal thee, thine, etc.
In Shakespeare's times, this is how people spoke.