I have a 10 year old chow. She has lost weight and her hair is thinning and she is going pee in the house at night, which is not her at all. She would be appalled to go poddy in the house. She eating great and doesn't seem sick.

She's getting old. She may have something treatable, she may not. It could just be a UTI and a simple skin condition, or it could be serious. Only tests will tell.
We all have to prepare for the all too short lives of our beloved dogs.

At her age I would have her checked by the vet. There are just too many options out there. Is she on a regualr worming medication?

I would maybe take her to the vet and get her checked over. Maybe she is becoming cushanoid?