Apex domains cannot have CNAME records.
Question and response
Question
dig cimbbank.com.sg. NS
Answer
cimbbank.com.sg. 4 NS ns7.cimb.com.
cimbbank.com.sg. 4 NS ns6.cimb.com.
cimbbank.com.sg. 4 NS ns3.cimb.com.
cimbbank.com.sg. 4 NS ns3.cimbbank.com.sg.
cimbbank.com.sg. 4 NS ns4.cimbbank.com.sg.
cimbbank.com.sg. 4 NS ns5.cimb.com.
cimbbank.com.sg. 4 NS ns2.cimb.com.
Authority
The response has no authority records.
Additional
ns5.cimb.com. 4 A 203.153.95.47
ns6.cimb.com. 4 A 203.115.237.51
ns7.cimb.com. 4 A 49.50.12.166
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0