An Australian passport holder arriving in Thailand on July 12th for 15 nights appears to be eligible for the visa exemption. Travelers are generally required to show proof of onward travel and funds (20,000 THB or equivalent cash). Concerns about questioning at immigration seem to depend on the traveler's recent entry history.
Anyone can be asked for proof of funds (20K baht or the equivalent in CASH), proof of onward travel and proof of a hotel booking.
With that being said IF you don't live here on back-2-back visa exempt or tourist visa entries you're not likely to be questioned at all when you stamp in.
James ********
Looks OK to me if you do not have a recent history of entries back to back into Thailand.