I am finishing up a part time masters degree at a mid tier state school. I am really interested in moving on to a PhD at the same institution. I have enough credits beyond the masters and I have a science related role at a large company. I was hoping to kill two birds with one stone by somehow carving out a topic that would leverage my current work. I would self fund obviously, but I wanted to ask the community to see if anyone had been successful in merging work with their thesis topic. Also what is the best way to try and set up a scenario where one works and completes a thesis level project?
It sounds like it's time for you to have a chat with one or more possible advisors to start exploring possible research areas. One of the most important roles a PhD advisor plays is helping the student find and define a research topic.
Looking in my crystal ball at your future, here's what I see: a very small chance of being able to kill two birds with one stone. It could happen, if the stars all align in a very fortunate way; but please don't count on it. For thesis research, you have to be free to follow your nose. You can't afford to box yourself in.
You may want to consider a somewhat different approach from the self-funding idea, and apply for a teaching or research assistantship (and quit the job), or get your present company (or some other company) to pay at least your tuition, with an agreement that you will work for them for x years after graduating.