I would imagine Kim is on a perpetual hunt for Chinese spies within his organization - possibly South Korean, but most likely Chinese.
China is the only country with any control or influence on North Korea. China the only country that has business, government or military contacts with North Korea. They share a border with millions of ethnic Koreans on the Chinese side
Do you think the CIA could get spies inside Kim’s government? No way - but the Chinese can.
Kim fears China more than anyone.
And didn’t the PRC just announce that it’s cutting off purchases of NK coal? Through the end of the year, anyways.