We came back from Thailand last week but could not buy alcohol at duty free in Thailand, For some reason you can't buy it in Thailand airport and take it through, if not already purchased and put in your luggage then you can only buy it at duty free Australia.
I had bought some spirits and had it in my suitcase, but was planning to buy the rest at the airport. so I got a little bit. If I was you I would purchase it before and put it through with your luggage because it is miles cheaper in Thailand than at our duty free in Australia
We had no problem buying cigarettes but not alcohol.
Maybe you can check up before you leave in case the people from Kings Duty free Thailand put us on a bum steer. Up until this trip we had no problem buying our alcohol in Thailand duty free.