Sometimes you can find stuff like this at an office store like Office Max, Office Depot, Staples, etc…or an electronics store Best Buy, Circuit City, Radio Shack, etc…
There are 2 separate issues: wattage and plug type. If you have the right type of wattage on the device you need to use, you probably only need a plug converter. If your appliance has a different shaped-plug and different voltage than the standard in the country you are going to than you need a voltage adapter and a plug converter. Here’s a website that gives the voltage, frequency, and plug outlet type for Thailand: http://treehouse.ofb.net/go/en/voltage/Thailand
That should help you know what to buy depending on where you’re going and what devices you plan to use.