I travel to Thailand 3 or 4 times per year and having a cell phone with a local number saves me a lot of money. Local calls are dirt cheap and long distance calls back to America are inexpensive.
All you need is an unlocked GSM tri-band or quad-band phone a Thai SIM card. A SIM, or subscriber identity module, is that little wafer chip about the size of your thumbnail under your battery in your cell.
You can get SIMs in almost every country you travel to and it only takes a couple of seconds to swap them out.
The problem with American cell phone carriers is that they lock the SIM to a specific carrier. So, you have to get it unlocked, a relatively simple task that will only cost a couple of dollars. You can try to get your service provider to unlock your SIM, but most likely you will have to be a long time customer with a compelling story to get it unlocked.
The easiest way to overcome this is to buy a cell phone in Asia. They are inexpensive and are not locked to specific carrier. New and second-hand phone are readily available and the prices are very reasonable.
The only real problem I have had is maintaining the same phone number in Thailand trip after trip. The way it works in Thailand, is you get your SIM, and then to add more money to it, you go to the local 7-11 or Family Mart, and buy a small, credit card sized, phone card. You scratch off a protective coating to reveal a series of numbers that you input into your phone. Whatever denomination of Baht you purchased is automatically added to your SIM. The company will also extend the length that your SIM is valid for.
In Thailand, for every 300 Baht (about 9 US dollars) added to your phone, you get one additional month of usage. My problem has been having enough months left on my SIM to keep my phone number for my next trip. My trips can be three months apart or sometimes six months. So I need to ensure that there is ample time on my SIM.
This trip I learned how to overcome this. I use a service called 1-2-Call and all that has to be done is to have someone with an abundance of months on their phone that they can transfer to you.
My girlfriend had a bunch of months on her phone, so she just called *140 and followed the prompts to transfer time a month at a time. I had her add 8 months to my SIM card and it only took a few minutes to conclude the swap. You can choose English or Thai and the instructions are very easy to follow. Just keep in mind that when they prompt you for “validity” this means how long the card is valid for.
I also found that I can use the same number to swap money from my phone to hers. I had a lot of money on my phone because I would try to increase the amount of months by adding about 1,000 Baht to my phone in hopes that I would have enough time to last me until my next trip.
In the past, I would buy phone cards for her so that she would have time and money on her phone to call me when I am back in America. This worked out even better. She got money added to her SIM and I got time. Definitely a win-win situation.