I have used a variety of store-bought ant killers to get rid of them inside. One of the best seemed to be a gooey substance that you put out which really seemed to attract them. Can't remember the name of the product. Of course, I have also discovered that there are different types of ants that require different types of ant killer. I alway carry fire ant powder - Greenlight is my favorite - to use outside.
A long time ago someone told me that when ants are getting in from outside you should sprinkle Comet, (I'm sure any brand of scouring powder would work) around the jacks, water and sewer hoses, electric cord and anything else that they can crawl up and enter the RV. It has seemed to work for me.
One time we were parked under a tree and the branches just barely brushed the roof. I discovered that trip that they can also come from trees, so I'm careful now that no branches even come close to the RV.
Hope this helps.