North Korea is a threat to South Korea, Japan and even Russia, considering that they do have missile technology that can easily strike them given the chance. Also, China does have their back, {for now} so that gives them the stones to make threats knowing that a pre-emptive strike on North Korea could easily turn the Korean Peninsula into a nuclear wasteland, and can only get worse from there. Also remember that North Korea has been all talk for a long time, and until they fire the first shot, then they are simply an annoyance, and not a target for nuclear elimination.
The one wild card is China, largely because they do have the back of North Korea now, if NK does attack SK, then a retaliatory attack will be imminent, and then the Chinese will back out and leave NK as a sacrificial lamb to the nuclear fryer. China wouldn't dare to threaten their best economic customer, and even with their "million man army", they don't stand much of a chance against America in a toe-to-toe fight, especially when nuclear weapons get involved. No sane leaders within the Far East want to be near North Korea if they attack, because everyone else not named China will turn them into toast within a matter of time.