I love to fly to Thailand with my furry friends. There are certain formalities to be made. You need to get through veterinary control / registration first. Veterinary documents are being checked there. The cost is several hundred THB. Then you are free to go to customs, where import permit should be waiting for you. This should be processed in advance by the receiving party. The cost is several thousand THB.
As always don’t even try to be on the wrong side of the law