From western media it is around 10k North Korean soldiers and from the same source Russia is recruiting 30k troops per MONTH. Those are people voluntarily signing up. The Russians seem to be following a low level of force commitment and a grind them down strategy. That is the Russian philosophy of war. The Russians are keeping much of their military in reserve for the possibility of having to take on all of nato. Ukraine never had a chance.
I don't know the accuracy of the amount, but I've heard that Russia has had around 650,000 casualties (dead and wounded) since the conflict began. If that is right, they probably need 30,000 a month.