SK has a fairly strong economy and good technology. America has slipped seriously in their view because of bam bam.
The NK military is big but not all that well trained or equipped. Their special forces are pretty good because they do real world stuff against SK fairly often. They have a LOT of artillery and their main target is well within range. They also have significant chemical weapons that they can deploy out to about 800km if I recall correctly.
Eventually China and Russia will hedge their bets and side with the SoKos.