Well, North Korea benefits from getting experience and field-testing radios and winter underwear. The drone environment is very good advertising for their goal of becoming a major arms dealer.
Yes, North Korea gains immediate benefit (money or material aid) and a theoretical delayed benefit (demonstration of mercenary abilities, and real world experience for their troops if they survive). Russia gains bodies to throw against bullets. If every North Korean soldier died but took several bullets for Russian soldiers, it's a win for Russia. They do not care about the North Korean soldiers or North Korea.