Pre order is certainly available in Business. I just did it successfully for SIN-BKK-KTM-BKK-SIN.
Back indeed, and also buggy. AKL doesn’t show on the drop down list of originating cities and so presumably I could not pre-order, but TG492/491 AKL-BKK and vv are not on the list of ‘excluded’ flights (
https://www.thaiairways.com/en_TH/Ma...ing/CPOM.page?) .
I have had so-so experiences in pre-ordering (F or J) on a range of airlines, and just go with whatever is offered on the menu card these days.