mailman.ftpi.or.th has no NS records.
NS records for this zone are defined at ftpi.or.th.
NS records for this zone are defined at ftpi.or.th.
Question and response
Question
dig mailman.ftpi.or.th. NS
Answer
The response has no answer records.
Authority
ftpi.or.th. 1800 SOA pete.ns.cloudflare.com. dns.cloudflare.com. 2397393194 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0