An official from the National Statistical Office estimated, “”It seems that there are many cases where women originally of Vietnamese nationality marry Korean men, become naturalized, then divorce and remarry Vietnamese men.” Meanwhile, the number of Vietnamese men who came to Korea as a labor force and tried to settle there has increased,” he said.
https://www.joongang.co.kr/article/25227149
China seems to be an exception because of the ethnic Chinese.
Vietnam is leading the way.
https://theqoo.net/hot/4096872378