I feel like this must be fading because I lived in North Yorkshire for almost 5 years and never heard a thee/thou used. On the other hand, English dialects are hyper localized so there might be villages where it is normal.
> English dialects are hyper localized
On a vaguely related note, has anyone else (particularly in Yorkshire) use "seef"/"seefing" to mean "see if"/"seeing if" (as in "I was seefing/seeing if it was in the car")? I hear it all the time from my immediate family, but I've never been able to find it referenced beyond that.