[falko]

You can try nested locations for each folder, e.g. like this:

location / {
                try_files $uri $uri/ /index.php?$args;

               # Add trailing slash to */wp-admin requests.
               rewrite /wp-admin$ $scheme://$host$uri/ permanent;

               location ~*  \.(jpg|jpeg|png|gif|css|js|ico)$ {
                    expires max;
                    log_not_found off;
               }
               # Deny public access to wp-config.php
               location ~* wp-config.php { 
                    deny all; 
               }

}

Then try the same for a subfolder:

location /subfolder {
                try_files $uri $uri/ /index.php?$args;

               # Add trailing slash to */wp-admin requests.
               rewrite /wp-admin$ $scheme://$host$uri/ permanent;

               location ~*  \.(jpg|jpeg|png|gif|css|js|ico)$ {
                    expires max;
                    log_not_found off;
               }
               # Deny public access to wp-config.php
               location ~* wp-config.php { 
                    deny all; 
               }

}