I have been looking at flights to Perth to renew my O-A visa next month, due to the likely closure of the Consulate in October. Mox is included in my research mix, along with individual airlines, and flight search engines (the best of which I have found to be Skyscanner).
The results for Mox have been slightly mixed, although not badly so. On the Singapore Airlines site I can get a fare for 21865 baht, with Mox about 1000 baht dearer. However, they are about 3000 baht cheaper than the Thai Airlines site (22k v 25k).
As douglas flagged above, you need to add in credit card charges for Mox (about 3%) which you generally don't cop on the airline sites.
I also went through the exercise of doing a fully inclusive fare on Air Asia. What started out at 12,900 ended up at 16,000 by the time you added in decent seats (particularly KL to Perth), baggage, meals and refreshments.







