Apex domains cannot have CNAME records.
Question and response
Question
dig gasanalyzerthai.com. NS
Answer
gasanalyzerthai.com. 5 NS ns-985.awsdns-59.net.
gasanalyzerthai.com. 5 NS ns-1498.awsdns-59.org.
gasanalyzerthai.com. 5 NS ns-1200.awsdns-22.org.
gasanalyzerthai.com. 5 NS ns-1013.awsdns-62.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0