Ken was born in Japan to Thai parents. But Japan, where the nationality law is based on lineage rather than birthplace, considers him stateless.
He is one of an unknown number of children whose parents do not register them with their home countries or with Japan for fear of falling foul of the immigration control law.
The Japanese government's official estimate of 1,070 stateless children under the age of 14 is based on declarations in alien registration cards. But the real number is thought to be far higher.