1. DBS Bank 

DBS Bank is the largest bank by assets in Southeast Asia, with over 24,000 employees, 250 branches, and 1100 ATM machines across 50 different cities. DBS Bank was established in Singapore during 1968 and is a multinational bank and finance service. The bank is known to be the safest bank across all of Asia, providing a range of services such as consumer banking, business banking and private banking. 

Total assets (billions of US$): $491.9

2. OCBC Bank

Oversea-Chinese Banking Corporation known as OCBC Bank is a multinational finance and banking services company. First founded in Singapore during 1932 by Mr Lee Kong Chian, who mergerged the three banks (Chinese Commercial Bank Limited, the Ho Hong Bank Limited & the Oversea-Chinese Bank Limited) to form OCBC Bank. The bank has more than 570 branches and officers across the 18 countries they operate in, around 100 of these are located in Hong Kong. 

Total assets (billions of US$): $394.5

3. United Overseas Bank 

Founded by Wee Kheng Chiang in Singapore during 1935. The United Overseas Bank is an investment bank as well as a financial services, with over 500 offices across 19 different countries. The bank has 68 branches in Singapore alone along with its headquarters. In total United Overseas Bank has around 24,853 employees. 

Total assets (billions of US$): $326.7

4. Maybank

MayBank was founded in the year of 1960 by Khoo Teck Puat. It is a Malaysian universal bank which mainly operates in Singapore, Malaysia and Indonesia. Maybank is one of the most valuable banks in this area with 22 million customers. The bank also has 2600 banking branches along with over 43,000 employees in total. 

Total assets (billions of US$): $213.0

5. CIMB

Headquared in Kuala Lumpur, Malaysia, CIMB Group was first established during 2006. CIMB is an investment bank that has over 1,080 branches just within this region. The bank has branches and services available in 18 different countries with a total of over 40,000 employees. CIMB is the 5th largest Southeast Asian bank with over 16 million customers.

Total assets (billions of US$): $149.7

According to fintechmagazine.com

(https://fintechmagazine.com/top10/top-10-largest-banks-southeast-asia)