Issues with starting via NRPE

Hello,
The plugin is good. I changed it a little to return warning and critical values.

It works well if you start it on the local client side.

When you start it from a remote Nagios 3.5.1 server and call it with NRPE it returns always:
/usr/local/nagios/libexec/./check_nrpe -H hostname-xxx -c defined-command-xxxx

ERROR: Folder is invalid

It seems that the plugin cannot detect properly the folder that is set with NRPE

When I start it locally I have:
/usr/lib/nagios/plugins/check_folder_size.sh -f /path-to-folder-xxxx -s g -w 60 -c 80

OK: The folder size is 44GB |size=44GB;60;80;0

Can you please help me to find the problem with the NRPE?