Apex domains cannot have CNAME records.
Question and response
Question
dig thebusinessthailand.com. NS
Answer
thebusinessthailand.com. 5 NS ns2.thebusinessthailand.com.
thebusinessthailand.com. 5 NS ns1.thebusinessthailand.com.
Authority
The response has no authority records.
Additional
ns1.thebusinessthailand.com. 5 A 203.146.127.133
ns2.thebusinessthailand.com. 5 A 203.146.127.133
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0