GWANGYANG, South Korea—Abandoned, he feels, by three countries, Cho Guk-gyeong shows a visitor his South Korean alien registration card, which describes him as “stateless.” It’s an apt description of what his life is like in South Korea, 15 years after he fled North Korea. Most North Korean defectors to the South are ethnically Korean, but Cho, 53, is a third-generation Chinese immigrant. While ethnically Korean defectors are entitled by law to a package of benefits designed to help their resettlement in South Korea, Cho can’t receive that support because he maintained his Chinese nationality, even though his family has lived in North Korea for generations. “I don’t need a state subsidy or other assistance. I just want South Korean citizenship so I can work diligently until I die,” Cho said during an interview in the southern port city of Gwangyang, where he recently worked as a temporary manual laborer—his first …