mx03.mh.bkk1.cloud.z.com has no NS records.
NS records for this zone are defined at mh.bkk1.cloud.z.com.
NS records for this zone are defined at mh.bkk1.cloud.z.com.
Question and response
Question
dig mx03.mh.bkk1.cloud.z.com. NS
Answer
The response has no answer records.
Authority
mh.bkk1.cloud.z.com. 3600 SOA ns-a1.cloud.z.com. postmaster.example.com. 1510309953 3600 600 86400 3600
Additional
. 0 OPT ; payload 2800, xrcode 0, version 0, flags 0