Use this method to show message to logged user on remote computer:
psexec64 -s /user:domain\user -i \\[remote_computer] cmd /c "msg * < \\[computer]\share\message.txt"
Message from shared text file will be outputted on remote computer.

Use this method to show message to logged user on remote computer:
psexec64 -s /user:domain\user -i \\[remote_computer] cmd /c "msg * < \\[computer]\share\message.txt"
Message from shared text file will be outputted on remote computer.