
Richest man: Sultan Haji Hassanal Bolkiah
Ethnicity: Malay
Industry: Oil & Gas
Net Worth: $25 billion
Source of Wealth: National wealth
*Note: No data on commoners' wealth and foreign sources always attribute him as as country's richest.
Cambodia

Richest man: Oknha Kith (Kit/Keith) Meng
Ethnicity: Chinese-Khmer
Industry: Investment, Development & Construction
Net Worth: Est. $500-700 million
Source of Wealth: Self Made
Indonesia

Richest man: Robert Budi Hartono (Huang Hwie Thong)
Ethnicity: Chinese
Industry: Cigarette
Net Worth: $7 billion
Source of Wealth: Self Made
Laos

Richest man: General Khamtai Siphandon
Ethnicity: Lao
Industry: Miscellaneous Business Activities
Net Worth: Est. $800-860 million
Source of Wealth: National wealth
Malaysia

Richest man: Robert Kuok Hock Nien
Ethnicity: Chinese
Industry: Agricultural plantation, Conglomerates/Multi-Industries
Net Worth: $12 billion
Source of Wealth: Self made
Myanmar

Richest man: Tay Za
Ethnicity: Bamar
Industry: Airlines, Conglomerates/Multi-Industries
Net Worth: Myanmar secrecy means wealth cannot be correctly estimated, est. $200-300 million and can be far more
Source of Wealth: Connection to Myanmar's dictator
Philippines

Richest man: Henry Sy Zhi Cheng
Ethnicity: Chinese
Industry: Shopping Mall
Net Worth: $5 billion
Source of Wealth: Self made
Singapore

Richest man: Wee Cho Yaw
Ethnicity: Chinese
Industry: Banking
Net Worth: $3.6 billion
Source of Wealth: Inherited
*Note: Singapore richest and 2nd richest man have died and fortune distributed among descendants, hence before the next official list I put the 3rd as richest.
Thailand

Richest man: Dhanin Chearavanont
Ethnicity: Thai-Chinese
Industry: Communication, Conglomerate/Multi-Industries
Net Worth: $7 billion
Source of Wealth: Inherited
Note: Thai King worth $30 billion, but Forbes list placed him as nation's richest
Vietnam

Richest man: Truong Gia Binh
Ethnicity: Viet
Industry: Technologies
Net Worth: Est. $850 million
Source of Wealth: Self made