Mate just come in on a Non O visa from the Thai Embassy in Aussie. Once here head to Thai immigration and get the heads up on what you have to do. You can open a Thai bank account on an O visa. Just go into any branch, I use Bangkok Bank and Krungsri. Both same same. Take ya passport clean clothes, shoes, freshly shaven. Tell 'em you want to open bank account and thanks but you dont want their insurance. Get atm card at same time. Deposit a hefty amount of au dollars. Tell 'em you are looking to purchase a condo. ..and away ya go. Welcome to Thailand. 👌
Go into Bangkok Bank of Krungsri. Take your passport, be well dressed, no shorts, no tee shirts, clean shaven. Tell them you are looking at condos / going to buy a condo sometime and you want to set up a bank account so that you can send over 3 or 4 million baht. Thats how I did it back in the day. Good luck.
Once your 90 days is up step out of Thailand for a few days. Fly down to KL for a couple of nights then return to Thailand. You will get another 60 days visa exempt entry and then extend that by another 30 days. 180 days all up.
I must be doing something right. As I said I have never been pulled aside..and I have routinely carried a lot of cash thru immigration. I will continue to do so. It is mine. Ive earned it and I paid tax on it.