Several thousand North Korean soldiers training in Russia - this is how they will potentially deploy to Ukraine:

Russia currently denies presence of NORK troops fighting in Ukraine. Instead they will place them all in Russia at numerous training exchange program sites. Then one of those sites will be hit by a secret “false flag” type attack. Then North Korea will declare it’s right to be able to fight back and will join the war as an attacked country, whose troops were massacred while training peacefully in Russia, with Ukraine the accused aggressor.

Source to Info-Blurbs acknowledges a secret transfer of up to 25,000 NORK soldiers into Russia for friendly partnered training activities, over past several months now.