spfext.spf.ksc.net has no NS records.
NS records for this zone are defined at spf.ksc.net.
NS records for this zone are defined at spf.ksc.net.
Question and response
Question
dig spfext.spf.ksc.net. NS
Answer
The response has no answer records.
Authority
spf.ksc.net. 3600 SOA ns1.ksc.net. hostmaster.ns.ksc.co.th. 2019122417 3600 900 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0