There's a holiday coming up
23 October (Tue) King Chulaongkorn Day National Holiday
If you're heading in on that day(or the day before),get a bottle of what you like from Airport Duty Free,or on the plane.If you'll already be on the ground,stock up at 7-11,supermarket,etc..
Don't get caught searching for booze on the day,have your "fix" ready!