Dad has painful arthritis and won't go to the doctor. And he smokes. I am scared he is going to die one night. Any advice?

Mutley, you can try to add items to his diet that help make his system more alkaline. That helps with arthritis pain.

Fresh squeezed lemon in water, apple cider vinegar with the mother and raw honey mixed with water are both helpful and nutritious to boot.

Enjoy the time you have left and prepare yourself for the fact that he will probably die before you. It is difficult and it is very sad, especially when you are close but, it is part of life.

So find ways to create happy memories and don't sweat what you can't change.

We are all going to die some night, or some day. I am unclear as to what you feel now is going to be the cause of your Dad's imminent death? Are you thinking arthritis causes death? It doesn't. It can affect pain and mobility. Are you afraid he will fall asleep with a cigarette? He is unlikely to stop smoking at 83, and frankly, why would he?
I am unclear exactly what concerns you and what choices in your life are affected. More specific question might help. None of us look forward to the time we will lose our elders, but it is a certainty, if we don't first die ourselves, that we will. I am uncertain what exactly you are dealing with.

If your dad is mentally sound it’s his choice to smoke and refuse medical care. Honestly, there’s no cure for arthritis and we’re all going to die sometime. Please accept both realities. I lost my dad last summer, it was and is painful, but I knew and accepted that it was coming. There are some good meds to help with arthritis pain, I hope your dad will decide to pursue it, but if he won’t you’ll need to decide to enjoy the time you have with him