According to this and other tweets Minseok is working as a DMZ Police member (in the Demilitarized zone along South and North Korean border), based on the black tag he's wearing on this latest pic. Stay safe Minseokie!

The DMZ Police is a special military police unit allowed to guard and patrol the DMZ unlike civil police that can't enter those grounds. It is considered one of the most dangerous and difficult jobs for soldiers because of all the tension and risks involved.

Soldiers and who work as DMZ Police go through intense training. Only a number of people are allowed to work at the DMZ at the same time so out of all the enlisted soldiers only a handful will actually experience working there.

There's a lot more information about this that can be found online but I recommend people who tend to get anxious to not look it up. Let's just say it's a difficult and somewhat dangerous job due to all the political tension involved and hope Minseok finishes his work safely!