The deaths of hundreds of mainly undocumented Thai migrant workers in South Korea have been uncovered by the Thomson Reuters Foundation, prompting the United Nations to call for inquiry into the fate of migrants known as "little ghosts."

At least 522 Thais have died in South Korea since 2015 — 84% of whom were undocumented — according to data from the Thai Embassy in Seoul obtained via a freedom of information request.

Four in 10 deaths were recorded as due to unknown causes while others were health related, accidents and suicides.