I did similar with CBA, but they issue an up-to-date statement. Actually, I did it a couple of times, due to my impatience and/or anxiety. As a result, my final statement only had 2 days of transaction history (nothing!). I uploaded it as it was and it was accepted with no issue.
Sign up and start the application process now, from wherever you are.
Finish it, pay and submit when you're there.
I'd recommend considering the processing time that they give, rather than planning travel around what others have experienced. Unfortunately, there is no fixed processing time.
The application process will ask you to specify your travel plans. It seems that if you're planning to enter Thailand 'soon', you're application might be processed 'sooner'...
Have you tested that? I've been back online several times, but never went past the first screen.
I'm surprised that they'd create separate downstream forms for different countries, when the fundamental requirement 'should' be the same, but it's obviously doable...