What can “the west” really do to prevent or stop troops from NK being sent to the Ukraine front?
Stop sabotaging peace talks, pressure Ukraine to accept the terms as they exist now before they get worse, lift the sanctions on North Korea in order to incentivize them to integrate with the rest of the world, withdraw US military equipment from South Korea. Kim Jong Un is often presented in American news like a crazy person, but truthfully he (and the rest of the actors in the North Korean state) is a rational actor and the “hermit kingdom” is not an aspirational goal of the DPRK but a state of affairs that has been forced upon them by decades of sanctions and isolation - give them a reason to be neutral, and assurances that they won’t be stabbed in the back (as they have been in previous deals with Western countries), and there’s a good chance they’ll take it.