When executing a ksh script under sudo and sudo has a line to verify the checksum, then the $0 is reported as /usr/bin/ksh instead of script being interpreted:

ksh script /usr/local/bin/script.ksh

#!/usr/bin/ksh
echo "\$0: $0"

configure sudo to verify the checksum

# echo "kshuser ALL=NOPASSWD: sha256:$(sha256sum /usr/local/bin/script.ksh)" > /etc/sudoers.d/kshuser

execute the script under sudo

(kshuser) $ sudo /usr/local/bin/script.ksh
$0: /usr/bin/ksh

The root cause is likely due to having a execveat() being used by sudo to execute the script, instead of "regular" execve(), as seen with stracing:

5129  11:25:59.445250 execve("/usr/bin/sudo", ["sudo", "/usr/local/bin/script.ksh"], ...
 :
5131  11:25:59.489322 execveat(6</usr/local/bin/script.ksh>, "", ["/usr/local/bin/script.ksh"], ..., AT_EMPTY_PATH) = 0

The execveat() is done on purpose to make sure the script was not altered.

Due to this bug, it's impossible to know which script is currently executing.