What is the best way to access 200,000 THB from Australia to buy a car in Thailand without a local bank account?

Why not just deposit the funds onto your Aust credit card, and buy it with the card (Assuming you are getting it from a dealer), I did that to pay a hospital bill. (I rang the bank and told them before hand)

You can transfer the funds from wise to a thai bank, save you a lot of 220 baht withdrawal fees

If it was me I would probably spend the 4k and get an agent to assist you in opening a bank account . Then transfer directly with Wise or a similar company. Remembering you can take $10,000 in cash out of the country, and if you need more just fill out a simple form and hand it in after you clear passport control. Well that's in Melbourne not sure about other airports. But you're already in Thailand so that might be advice for another trip.

Using Wise card at ATM has high bank fees- if you have a Thai partner with a bank account transfer to that bank with Wise card is the cheapest way

You can send yourself the funds online using Western Union and similar services so you can get the cash in the one go, ATMs will charge you about 220 THB for every transaction plus money conversion fees also at your Australian bank end and ATM transactions are limited to a specific cap, depending on the bank you are using to withdraw cash from so you would have to do multiple withdrawals with multiple charges and some ATMs will flag multiple withdrawals and will either block and retain the card or simply put a hold on it until you contact your bank and explain that you are indeed in Thailand and that you are actually withdrawing funds yourself and it's all legit. The alternative would be to walk into a big branch and tell them you want to withdraw that much from your account overseas, I did it decades ago and there was no problem but things may have changed ...

Wise charges fees too…

I use my Wise card/account to pay rent, purchase items etc… For me it’s cheaper to withdraw cash from my Australian 🇦🇺 bank account as they don’t charge any ATM withdrawal fees. We all have to pay the 220B of course when withdrawing cash from a non Thai bank account.

Are you alone or do you have a Thai partner here? If you do, transfer the money (Wise) to their account and withdraw if from there. That's how I get money here without any fees minus the Wise costs.

I would have taken 10k aud cash

If it's a large sum, sending western union to yourself MIGHT end up being cheaper than Wise with multiple ATM fees. Especially if you haven't used it before as the first time doesn't incur fees

Wise if you have a thai bank too.

Or....there is this Nigerian prince who....

I Talked To The Bank Manager Of Bangkok Bank In 2011' And Got The Limit That I Could Withdraw Raised To Over 100,000 Thb In One Day.

ATM or try Krungsri inside sometimes allow 50k+

If you hit the yellow Krungsri ATM you can pull out 30k at a time. ATM fee will be 220 baht.. ..but, if your bank charges a foreign transfer fee then it isn't worth it and the Wise card is better. Good luck.

Wise is the cheapest way.