you were lucky then because they have been asking at bkk and asked everyone in front of me for their boarding pass as well, pain in the ass as some have on their phone and have to hunt for it.
when was the last time ? I come every 2 weeks and they have been asking for at least 6 months. Previously they had the tm6 and never asked for boarding pass
If your Aussie, go via Sydney consulate online pre-approval, you can write flights and dates your thinking about using, they do not ask for proof of the booking