There are several ways to get connected to the internet in Thailand. What is best for you will depend on several parameters. What are your speed requirements, where are you located, can you get a phone line etc...

The most widely used connection in Thailand is broadband through ADSL, however it is not always possible to get this type of connection. You might not be able to get a phone line at all, or the distance to the local telephone exchange might be too long to support ADSL. 

Mobile internet is poised to get some serious boost this year, several providers are  planning to roll out 3G networks, and in quite some area's you can get CDMA EV-DO either through CAT or Hutch, with real life speeds of between 400 and 800 kbps.

The GPRS network covers pretty much the whole nation, with the more populated area's having been upgraded to EDGE. Not fast, but usable, and wherever you are, fire up your laptop or PDA and you're on-line! 

Below is a list of articles detailing how to go about getting the different ways of getting on-line installed and activated.