Information on bringing pets (cats and dogs) to Thailand to accompany visitors to Thailand (personal not "for sale") can be found on the Thai Department of Livestock Development web site at http://www.dld.go.th/dcontrol/move/menu31e.html
and for the importation of dogs and cats please see their web site at http://www.dld.go.th/webenglish/movec1.html
Note: Web links for the Thai Department of Livestock Development are not working. We sent an e-mail message in this regard and hopefully the information will be available soon. Meanwhile, you can find the basic information on the web site of the Royal Thai Embassy - Finland
Please visit the web site of the Royal Thai Embassy, Washington, DC, for additional information including a link for the Import/Export Permit Form
Please note that you will need certification from the U.S. Department of Agriculture. This can be obtained from a USDA Animal and Plant Inspection Service Office - list of offices click here (PDF)
Be sure to read the information from the U.S. Department of Agriculture, "Travel with a Pet" and their "Frequently Asked Questions" section.
See additional helpful information at PetTravel.com