Thailand has a good mobile phone network, and there is good coverage particularly in Bangkok and other major cities. Mobile phone shops in Bangkok are everywhere! Mobile phone signals are usually strong, particularly in Bangkok.
Mobile phones are called precisely that in Thailand, along with smartphone or iphone. The term cell phone will generally not be recognised.
If you intend to purchase a mobile phone in Bangkok, then be aware that unlike many other countries, the full cost of the phone is expected unlike the UK where a new make or model is often provided free in exchange for signing up to a lengthy contract. There are good deals to be found at places like MBK. Whilst not to tar everyone with the same brush, please be mindful of the phrase if something is too good to be true, then it probably is.
There are three GSM mobile service providers:
Typical contracts are for 1 year, but are not difficult to break should you need too. Most service providers need to see a work permit, but DTAC only requires a passport and a credit card.
As with most countries, different price plans are available. There are some basic points you need to consider for choosing the right deal.
If your mobile phone is unlocked then it is possible to buy a prepaid sim which is available from most phone outlets at shopping malls. This can then be topped up at 7-11s and Family Marts.
Check the GSM operator's website (see above) to see whether your mobile is compatible.
If your sim card is locked then many of the mobile phone outlets at MBK and Khao San Road should be able to unlock it for you.
Alternatively, there are many cheap mobile phones which you could buy at MBK to use as a pay as you go phone.
Take care with pre-paid sims however. Many which grant access to the internet over their EDGE or 3G network charge for time and not bandwidth which can quickly drain credit.
Phone directory: Yellow Pages Thailand