They would need to be fast though because the economic situation for NoKor and vietnam is changing dramatically. NoKor population is clearly high iq. As with the vietnamese newest scientific insights gives them an iq of 100+.
These people probaly wont want to leave their home nations in the near future. (Compare SoKor, Japan, Taiwan, Singapore, western industry nations).
Fair enough. Should have been done at least 2 decades back. Now the labor emigration from Vietnam is declining as the living conditions back home are improving a lot. North Koreans may still be open to the idea of emigration, but I don't think that the situation will remain like that indefinitely. As you have pointed out, these people have high IQ, compared to the low IQ central Asians.