Well, it looks to me like they couldn't afford proper prime movers for their towed rocket arrays, so they went to some Agricultural depot and grabbed a bunch of rather ordinary Ag tractors to pull them with.
Sometimes it looks strange for me, when we see some weaponry mounted on the pick-ups or all-wheel-drive large trucks too. But in many cases it works for the users. I'm not a fan of N. Korea , but if a tractor may successfully tow the military equipment in the mountains, jungles with the absence of roads, why not to use them. I've heard Ukraine's DefMinistry nationalised the Ag tractors as well at the beginning of ATO, just don't know for what purpose.
Wow! Can't they afford a can of olive drab paint? Seems counter productive to have everything in camo, but then have a bright tractor highlighting your location.