Taking a slightly liberal view of 'exercises'. Could be drills, could be actual operations together.

https://apnews.com/article/north-korea-russia-military-cooperation-ukraine-china-55918dc4b8672a15ae103eb5fea2a930

Seoul's spy agency says Russia has likely proposed North Korea to join three-way drills with China

Russia has likely proposed that North Korea participate in three-way naval exercises with China, according to a lawmaker who attended a closed-door briefing with the director of South Korea’s top spy agency.