I have to say North Korea committing troops to Russia is confusing to me. North Korea's fertility rate is currently slightly below replacement rate, so every year that goes by the population of North Korean population shrinks. North Korea also does not have any option to increase its population via immigration.
North Korea should easily be able to see how Russia uses its own troops as "meat waves" and understand its own troops will be treated the same (if not worse).
They are a militaristic country with untested military. They need to seem dangerous so their saber rattling works. It used to work with nukes but people got used to that, so they want to become one of the countries with actual military experience they can then teach to other recruits