I’ve changed the script with the help of the following post - Sudo User access - and it’s working
folder create "{storage folder of client}/RunMe"
delete "{storage folder of client}/RunMe/output.txt"
delete __createfile
delete /tmp/bf_tmp_script.sh
createfile until __EOF
#!/bin/sh
echo Hello
__EOF
move __createfile /tmp/bf_tmp_script.sh
wait chmod 755 /tmp/bf_tmp_script.sh
wait sudo su - root -c "/tmp/bf_tmp_script.sh | tee {pathname of storage folder of client}/RunMe/output.txt"
delete /tmp/bf_tmp_script.sh