"Thou" is singular. "Thou people" is an oxymoron. The plural second person pronoun in Shakespeare's time was... "You."
Secondarily, using the singular second-person declension of the verb "wouldst" is correct only when speaking to ONE person. Second-person plural? "Would."
Sad that "You people would not believe" is correct Shakespearean English, but there you go.
Hey, I'm a writer. Words are my stock in trade.
To contribute:
Not only is this topical for INGO, but it has a funny. Look closely.
And another "boom" related thingie. How did no one ever think this was a wrong thing?