To use electric-powered equipment purchased in the United States or Canada, bring a converter and adapter. The electrical current in Vietnam is 220 volts, 50 cycles alternating current (AC); in Cambodia it's 230 volts, 50 cycles. In the north and other parts of the country, wall outlets take the Continental-type plugs, with two round prongs; they use both the two round prong and flat-pin plugs in much of the south. Many of the international hotels can provide you with converters and adapters.
If your appliances are dual-voltage, you'll need only an adapter. Don't use 110-volt outlets marked "For Shavers Only" for high-wattage appliances such as blow dryers. Most laptops operate equally well on 110 and 220 volts and so require only an adapter and a surge protector.
Blackouts sometimes occur, especially in summer, when everyone uses fans and air-conditioners. Hotels usually have generators, but you may want to keep a flashlight handy if you're staying in a minihotel.