The U.S. military has strongly suggested that they have the means to defend against a nuclear attack from NK.
As for what KJU is thinking? Well, he's insane. It's hard to say. Given the environment he's grown up in and his obvious lack of political savvy he seems to just be doing random crap to see what happens. NK has kind of turned into the fulcrum point that everyone has a finger on. It's not really about what KJU is thinking, but who he's listening to at the moment. It's really sticky because obviously someone should just go in there and clean house before people get hurt, but everyone else would get upset so nobody can really do anything.
I hear reports all the time that the people of NK are totally sold out communists and really hyped up to conquer the world. I have a hard time believing that a whole nation could be that delusional, but stranger things have happened.
Of course there's always the possibility that KJU is just crazy like a fox and NK is actually a giant theme park surrounded by jungle and funded by some genetically engineered tree that fruits gold nuggets. It would certainly explain why Dennis Rodman was so impressed.