You may wish to investigate an "Ufer ground" (after Herbert G. Ufer) or "concrete encased electrode". I'm quite surprised that these earthing methods are not common/permitted in Aus.
Our building steel (which is contiguous from roof structure into the driven piles) actually measures rather better than the 2.4m (ish) rod using my rather antique, but still functional earth resistance tester. Which probably explains the minimal damage incurred when we took a direct lightning hit to our roof.
It's important to understand that, like building regulations, electrical regulations tend to be tailored to local conditions (wet, dry, hot cold etc. etc.) and do not necessarily transfer well between locations. That said, AS3000 is a pretty good match for Thai conditions and methods, but, of course, cannot over-ride the local regs.