Depends upon where you park it and how accessible it is. Are you concerned about the entire camper disappearing? Or someone breaking in and ripping things off.
There are a couple things that will help detour a thief from taking the entire trailer. 1st is a hitch lock and second is a chain around the wheels. But a desperate thief can still have your camper out of there before you blink an eye, no matter how you try to secure it.
Items on the outside of the camper? like propane tanks, battery, tires? All you can do is put the battery inside the house or secure it so it's out-of-sight. Meth lab thieves will steal propane tanks. But here again, if you are really concerned, remove them and keep them out of sight.
One other thing you can do is buy an RV cover. It won't stop a thief, but if they can't see what under the cover, they might not take any interest in it either.
If you are worried about things getting stolen from the inside of the camper, just remove anything that has value to YOU. Even if that's your favorite tooth brush. Remove it and then you know it's in a better place.
A thief will get whatever they want. RV's are not very secure, no matter how much you try to secure them. All you can do is make your's less desirable than someone else's and make sure you have full coverage insurance on the camper. That's about the best you can do.
If you live in town, in a questionable neighborhood, then you might be better keeping it stored at a trusted friends house or a relative, even if that relative lives a considerable distance away.
In the end, all you can is keep your insurance paid up to date, and make your camper less desirable that one next one down the road. But if you have mischievous, ok... let's change that, if you have demon-destructive-juvenile-or-gang kids in your location, your camper probably won't stand a chance if you are gone, or even there. The best you can do is make sure you have vandalism and theft insurance paid up to date.
