How to find out from which folder a process is running?

Try this:

ls -l /proc/<PID>/cwd

Derived rom HUB's answer:

readlink /proc/<PID>/cwd

or even

readlink /proc/$(pgrep <program_name>)/cwd

You can't tell where a process was invoked from, only where it currently is. Look at the cwd ("current working directory") link instead of exe.