Thou requires a specific form of the verb, which always ends in - ( (e)s)t (e.g., thou art, thou wert, thou canst, thou thinkest, etc.), so the first sentence is not grammatical. The rest are fine. Since they are so archaic, however, you should be aware that it’s frequently not just a matter of substituting one word for another – in order for it to seem natural, you’d have to emulate ...
Thou art is normally shortened to thar/tha in Yorkshire - but thee, thar, thine are still relatively common, and useful if you want to refer to just one person. So "Don't thee thar me, thee thars them that thars thee" makes perfect sense oop north edit: my understanding is that the plural you/your originally was a polite form used to social superiors and thee/thine was the familiar (like tu ...
The old pronoun "thou" which had easily kept its original pronunciation when thorn was around, became "you." And since everyone who wasn't a scholar was completely confused as to the proper use of thee, thou, thine, and thissen to start with, and got even more confused when they were spelled with a "y," entropy took over...
Irregular past tense ended in -t goes this way: Thou leftst Thou departst Thou sleptst So far, when in doubt, I have searched actual uses of such conjugation in the corpus (or the internet), I usually find usages in 19th century books and sometimes in 20th century works, often translations, often from the bible and other classic books like the ...
Yahoo: 75th anniversary of 'How Great Thou Art' gives classic hymn a new verse