As described in a link below, conversion from markdown->latex->pdf with Korean language ignores spacing between words.

https://tex.stackexchange.com/questions/17292/how-to-write-spaces-between-korean-words-with-xecjk

One of the quick solution is the adding [space] option on xeCJK package as default. 

Several days ago, I made a pull request with a patch that adding [space] option on xeCJK as default. 

https://github.com/jgm/pandoc/pull/5855

I wonder other CJK language user also experiencing same issue and agree with this solution. 

Please give some feedback about.