If you got an unlocked mobile phone it is possible this will work for you in thailand provided you have the correct sim card when you get there. Telecoms are one of the more expensive things in Thailand so it is essential to prepare.
If however, you feel your mobile phone is too expensive to take traveling and you just want something cheap it is worth while exploring your options before you travel. Mobiles in Thailand as I have mentioned are on the costly side. However, if you visit companies such as carphone warehouse it is possible to get a basic pay go mobile phone from just £2.95. There is a small catch with this phone and that is you need to add a Tenner top up before you can own it! The reason why I suggest carphone warehouse is because all their mobile phones are unlocked and this makes placing a sim card for thailand within them a simple process as you dont have to find an unlocking code.
One point you will need to remember is that I do suggest getting a cheap mobile, but you do need to be aware that this needs to be a worldwide usable phone. How you will know if this phone will be suited is by checking its specification and see if it is a QuadBand Phone. If it is then your all systems go!
The phone in the picture above is the actual style of handset available for just £2.95!