Originally Posted by eccentricfusion

For one week, all the prices are fairly similar. Just go with the network you like or what line is the shortest. Coverage is about the same in major areas, speeds are similar as well. The cheapest option would probably be picking up a SIM at 7-11 and doing a top up for a few dollars, but it might be a little difficult if you can't speak or read Thai. It's not going to be a substantial savings going that route, especially just for a week. There are tourist SIMs available very cheap at the airport and you get the peace of mind that everything is working before you walk away from the booth.