How to make a passive income?

When a person wouldn't like to take any risk of loosing money, there is a common method of making regular income which is available to anyone in Vietnam. That is... depositing money into your bank account.

@Hachiya: but our VND is decreasing day after day......we still lose money :) but that is the good decision at this current economy.......

P.S. Thanks for the comments. There are risks associated with depositing money into Bank such as lowering VND exchange rate and security for the amount of deposit.
However, those risks are common to all of the people having income in Vietnam, like no one can escape from the rain.

@Kenji, all,
YOU CAN ESCAPE FROM THE RAIN! with the umbrella or better a car.
When you deposit money to a big VN bank, the kind of "too-big-to-fail" means their foreign partner will rescue them or better the government would not like Vietcombank to go bankrupt with millions of bank depositors rioting.
When you deposit at a foreign bank like HSBC/Citi, you may get only 16% rather than 19% at Can tho rural bank, but UK or US head-office of Citi will not let you lose your deposit, because they don't want this little Vietnam operation to spread the bad news worldwide that HSBC depositors can lose their money.

NB. This is probably the reason why, wealthy Vietnamese prefer cars/big-foreign banks

Hi Pascal., It's seem that you have been misunderstood the point of view from Kenji. He talking about the exchange rate. This is a big problem when the US keep going up again VND. Even you can negotiate with banks for higher interest you still have to take the pain.
As you can see on February 2011 when the state bank break the rate 8.5% from 18.932 to 20.693 for an US dollar, all the investors, especially Foreign Investors have to take that risk, all the equity have been down for 8.5%for a night, this is very painful.