Apex domains cannot have CNAME records.
Question and response
Question
dig CIMB.com.sg. NS
Answer
CIMB.com.sg. 5 NS ns6.cimb.com.
CIMB.com.sg. 5 NS ns5.cimb.com.
CIMB.com.sg. 5 NS ns7.cimb.com.
Authority
The response has no authority records.
Additional
ns5.cimb.com. 5 A 203.153.95.47
ns6.cimb.com. 5 A 203.115.237.51
ns7.cimb.com. 5 A 49.50.12.166
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0