The DTAC tourist SIM is quite a good choice for tourists coming to Thailand.  The 299 Baht version is especially good as it saves you from having to add credit right away.  Just buy it, put it in you phone and start using internet.

Feature of the 299 THB SIM:

  • 7 days unlimited 3G Internet – after the 7 days, sign up for a 3G package OR pay 10 thb / MB
  • Dual cut sim is both Micro and Regular sized (sorry, not a nano sim for iPhone 5 users)
  • Valid for 35 days after activated – once you top up, you’ll get more validity
  • 100 thb of calling credit
  • No registration requirements
  • Free incoming calls and SMS
  • Instant activation

More details on the DTAC Tourist SIM.      Get it with Amazon Prime and free shipping in the US.
dtac tourist sim