As you want I am here giving you address of the branch of Citibank which is located in Nex

Citibank Nex branch Services offers :
Deposits
Investments
Insurance
Loans
Global Executive Banking
Citigold

Address :
Citibank -Nex
Nex #LB1-02,
23 Serangoon Central,
(S) Singapore 556083

Some other branches of CitiBank in Singapore:

Punggol Branch
Address:
83, Punggol Central,
Waterway Point, #01-17,
Singapore 828761

Serangoon Gardens Branch
Address:
53 Serangoon Garden Way,
Singapore 555949

Woodlands Branch
Address:
30 Woodlands Avenue 2,
#01-42/43, Singapore 738343
(beside Woodlands SMRT control station)