In what region is "thou", etc. used in dialect?

I grew up in West Lancashire (near the Yorkshire border), and pretty well every one of my parents generation used thee, thou, thy and thine. The first three were sometimes combined into a multipurpose “tha”.

Along with this perseverence of the informal second person singular, the equivalent verb form was still often used, e.g. “where goest thou?” instead of “where are you going” and “what dost tha want?” instead of “what do you want?”.

It can still be heard in the Lancashire/Yorkshire region particularly, in rural areas.

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/vous or du/sie). Gradually everybody adopted the more formal/polite form to sound gentlemanly. Quakers and similar groups deliberately used the familiar thou form to show that they believed everyone was equal.

Yorkshiremen (and women) continued to use the familiar form because nobody is their social superior.