Apex domains cannot have CNAME records.
Question and response
Question
dig ksc.net. NS
Answer
ksc.net. 5 NS ns4.ksc.co.th.
ksc.net. 5 NS ns-v6.ksc.net.
ksc.net. 5 NS ns1.ksc.net.
ksc.net. 5 NS ns2.ksc.net.
ksc.net. 5 NS ns4.ksc.net.
ksc.net. 5 NS ns5.ksc.co.th.
ksc.net. 5 NS ns9.ksc.net.
Authority
The response has no authority records.
Additional
ns1.ksc.net. 5 A 203.155.5.1
ns2.ksc.net. 5 A 203.155.5.2
ns4.ksc.net. 5 A 52.230.104.11
ns-v6.ksc.net. 5 AAAA 2405:a000:9000:12:203:155:5:3
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0