The electrical current in Thailand is 220 volts, 50 cycles alternating current (AC); wall outlets take either two flat prongs, like outlets in the United States, or Continental-type plugs, with two round prongs, or sometimes both. Plug adapters are cheap and can be found without great difficulty in tourist areas and electrical shops. Outlets outside expensive international hotels are rarely grounded, so use caution when plugging in delicate electronic equipment like laptops.
In Cambodia, Laos, and Myanmar the electrical current is 220 volts AC, 50 Hz. In Laos, outside Vientiane and Luang Prabang, electricity is spotty, and even in Luang Prabang there are frequent late-afternoon outages in hot weather. In Myanmar, locals joke that Yangon (Rangoon) is so advanced, the city has power six times a day. Actually, many cities throughout the region suffer power outages as development and demand exceed supply.
Consider making a small investment in a universal adapter, which has several types of plugs in one lightweight, compact unit. Most laptops and mobile-phone chargers are dual voltage (i.e., they operate equally well on 110 and 220 volts), so require only an adapter. These days the same is true of small appliances such as hair dryers. Always check labels and manufacturer instructions to be sure. Don't use 110-volt outlets marked "For shavers only" for high-wattage appliances such as hair dryers.
Walkabout Travel Gear. Walkabout Travel Gear has a good coverage of electricity under "adapters," and other international travel tidbits. www.walkabouttravelgear.com.