Apex domains cannot have CNAME records.
Question and response
Question
dig thai-tva.org. NS
Answer
thai-tva.org. 3 NS ns-424.awsdns-53.com.
thai-tva.org. 3 NS ns-184.awsdns-23.com.
thai-tva.org. 3 NS ns-506.awsdns-63.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0