gw-relay.th.com has no CNAME records.
Question and response
Question
dig gw-relay.th.com. NS
Answer
The response has no answer records.
Authority
th.com. 3600 SOA ns.ksc.co.th. hostmaster.ns.ksc.co.th. 2026021200 3600 1200 129600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0