I have personally used all the ones cited below:
recent purchase
http://www.amazon.com/Insten-Univers...words=adapters
recent purchase, comes with built-in usb connector
http://www.amazon.com/Tripshell-WORL...ravel+adapters
bought many years back for $35, now under $20
http://www.amazon.com/Universal-Inte...ravel+adapters
They will work definitely in Vietnam/Thailand; no experience in Cambodia or Laos
Edit: these are all-in-one universal adapters; should work perfect worldwide.