The Countries Hosting North Korean Migrant Workers
North Korea
The letter was penned on June 29, the day Trump tweeted that he wanted to meet Kim at the DMZ in order to shake hands. The world of North Korean laborers abroad is a shadowy one and thousands of them get sent to different countries around the world to generate hard currency for the regime. Website "North Korea in the World" maintains statistics about the countries hosting the migrant workers.
Most of them go to China and Russia which are estimated to host a maximum of 80,000 and 40,000 laborers respectively. The vast majority of them are employed in construction, agriculture, logging, garment-making and traditional medicine while a smaller number are known to work in North Korean restaurants. Altogether, it is believed that 41 countries host or have recently hosted North Korea's migrant workers.

Description
This chart shows the countries believed to currently host or that have recently hosted North Korean migrant workers (2018).