You are right there is no duty free shop after immigration in Bankok unlike Sydney and the officials are strict I lost my toothpaste because the tube was too large even though it was almost empty.they also went through our carry on bags after they had been xrayed.We bought our duty free when we arrived back in Sydney before passport controll,we arrived back 22June so this is upto date.The problem going to Phuket is if you change flights you cant take any containers over 100mls onto the next plane.We stayed in Bankok 4days so just put our duty free from Sydney in our checked in luggage when we went on to Phuket.