Yes, it's very important to note that in Thailand the voltage is 220. These days most of the Thai hotels where I stay can accept North American plugs, but unless your electronics are rated for both 110 and 220 (usually saying something like "Input: 100v to 240v"), you will need a CONVERTER. These days items like laptops, mp3 players, PDAs, mobile phones, electric razors, etc. usually can handle both voltages. Just check to make sure.

In more rural areas or older buildings you may still find that the outlets only accept the 2 round pin plugs. Also, if your device has a grounded plug, a 2-pin adapter may come in handy as in some places the outlets only accept 2-pin plugs.