If your lights are on then look out and see who it is and speak to them through the door without opening it.
If your lights were out and you were in bed, then I would ignore them. If they persist and knock again, then I would speak to them without opening the door and ask what they want.
If they tell you they see something wrong with your coach, just tell them you will take care of it in the morning.
If it is the law, ask them what the problem is and go from there. Don't open the door until you verify their ID at a window.
Do not open the door unless you are absolutely sure that the person has a legitimate reason to be there.
Our large dog barking usually diffuses any situation.
This has never happened to me in many years of travel. The only time I have been approached when parked at a rest area or truck stop has been during daylight hours and it was always another RV owner who wanted to ask about our dog or ask about our RV.
