Hi
First step is to pull all of the "ant food" out of the trailer. With nothing to eat, critters are much less likely to take up residence. If they do move in, with no food their population isn't going to explode on you.
Next up, there are very normal ant bait / mouse bait / alligator bait
gizmos available down at the local bit box store. A scattering of these in and around the trailer is likely to have an impact on the local population. As mentioned above, a local exterminator can do this sort of thing for you.
If you are heading in and out of the trailer a lot, flying bugs will be a problem this time of year. You can spray the area with this or that. It might help a bit for some sorts of pests. We use Thermacell gizmos right by the door to reduce the mosquito population at the entry point. That's not a practical thing to do long term ....
Fun !!!
Bob