I do this route (ex Syd). As the other OP said, stay in international transit. usually get all BPs in Sydney so there is no need to go to the transit desk. As you are in business from BKK to CPH, you will have lounge access. I use the Thai Royal Silk with the showers. I can sometimes be quite full so I shower there and then head off to the other bigger Thai lounge.The posting of your flight on the screens in the concourses can be haphazard so keep a good watch on the time. It's usually shown on the lounge monitors. You can get a good brisk walk in this huge airport and there is a vrey nice lounge for economy passengers called the transit lounge in which you can find a quiet corner in the thai lounges are full. The fun begins on the return journey where there is a long layover for the SYD connection, MLB may be better.