You can, or others can buy and send to you, just pay into their paypal account or such. You need a SIM and a refill card for each phone.
I think I will be there in a week and am happy to do for you but really you not need.
Go to any 7/11 or family mart and pick them up once you get to your hotel. It is a simple issue. Depending where you are going I'd use AIS for Bangkok / Chonburi and most developed areas but DTAC is better for up country and TrueMove is making headway in some parts of the country...