Truck off.Bed light, radio, inside lights come on intermittently drains battery?

You have some kind of issue with a body control module that handles the lighting system. This would be caused by either one of the many sensors that monitor door positions -- open or closed -- as well as the system overall. A good diagnostic test using a diagnostic tool that can read all vehicle systems for your Ford is in order. I suspect the problem will not be terribly difficult to find once equipped with what you need to test out the vehicle.