I don't think Kim Jong Un wants to commit suicide, but in the spirit of 1984 he needs an external enemy to maintain his grip on power, Trump is the perfect enemy, every threat he makes, just makes it that much easier for Kim Jong Un to drum up support and crush any internal opposition.
Trump is also flying blind, he has gutted the state department of it's most experienced people, and everything he does seems to be based on gut feel that his supporters want to hear, they love his tough talk, #MAGA.
I worry that the Trump has zero ability to back down, whenever he is confronted with one of his lies, he doubles down and lies even more.
That's dangerous in situations like this.