Nowadays that has changed, many people travel with their smartphones, TAB's and even laptops. And we want information at our fingertips. Luckily there are still places where there is no telephone signal or internet connection.
But well you are traveling and want to be "connected" while in Thailand. The most important thing is "DO NOT USE INTERNET ROAMING!". That is going to be bloody expensive.
So what are the other options?
First option "Keep your own SIM card and use Wifi"
Important with this option is that you will have to switch-off internet roaming on your telephone. For this see the settings of your device (TAB or smartphone).
In almost all Hotels, Guesthouses, Resorts, Coffee Shops and Restaurants is free Wifi. So you can use Facebook, your browser, read mail en chat via Skype, Whatsupp or Line. You can even make calls via Skype and Line. This is how did go around in Europe for 2 weeks.
Be aware that if you make a telephone call that call will be (semi)International. And when people call you, you will pay the international part of the call.
Second option "Get a local SIM card"
Important to realise is that the home front can not call you anymore on your home SIM card. Unless you have a telephone with dual-sim or if you have 2 telephones with you (or 1 telephone and 1 TAB).
You can buy sim-cards at the airport or at any 7/11 shop. Or at any shopping mall. Check if your device works on the Thai network system. Some shops will help you with the setup of your device.
There are basically 3 providers in Thailand : AIS, Dtac and True. There are all 3 good, some will work better or cheaper. Some have better coverage upcountry. I used Dtac for about 8 years, but when I moved to the mountains I need AIS because Dtac had no signal in my area. There are changing promotions from all 3 providers, just look at the moment you are traveling what is the best promotion for you.
Have a look at :
AIS Traveller SIM
TRUE Tourist SIM card
Dtac Tourist Packages