Bringing money from Australia

if you are bringing more than $10,000 in cash then you have to declare it at customs on your arrival, less than that no problem at all and you will be able to convert it in local  currency at any money changer or bank of your choice.
cheers

I agree with skyaslimit.

However if you don't fancy carrying a large amount of cash for safety reasons you could bring sufficient for your immeadiate needs. Set up a Thai bank account and transfer the rest using a Forex company and electronic transfer.

Most offer good rates(not as good as cash in Thailand)and if you transfer a big amount its free. In the UK its free to send money from a personal bank account to Forex company(not sure in your neck of the woods). They make their money by offering you a slightly lower rate than the interbank rate.

The recieving bank in Thailand will charge a maximum of 500 Baht.

Transfer the funds in your native currency and get the Thai bank to apply exchange rate.

Like I said at the start it won't beat the cash rate at somewhere like Super Rich in Bangkok but comes a reasonable second I think.

Hope that helps.

A couple of things I'll add to the conversation that you may want to consider as we are talking about $$$
Be careful of hidden fees when using cards at ATMs as there may be (2)fees, the ATM, and one from your bank.

The ATMs may offer to automatically convert the charge to your home currency. Refuse this option. This is Dynamic Currency Conversion and the exchange rate will be considerably lower (on the order of 5-7%) than the rate normally applied by your home bank. So if an ATM asks "Convert to [your home currency]?" just choose "no."

1)
Make sure I use a Credit Card that has No Foreign Transaction Fee when doing business..loose more money.

ex.)Barclays Arrival Card - (2)things going for it.
a)No Foreign Transaction Fees.
b)I got 40,000 Miles after spending $1,000 within 3 months, worth $200 or $440 when transrerred to an airline for a future flight.

2) on a side note, but concerning $$
When I travel from the states I try to:

1) Check out which airlines fly to my destination and try to match that up with a credit card promotion that earns miles in that Alliance (Oneworld,SkyTeam, or Star Alliance).

Then sign up with that carrier for their frequent flyer program and get their card to have my flying miles credited to my account, plus perks.

For me.. I applied for the American Airlines Citi® Platinum Select® / AAdvantage® Visa Signature® Card (One World alliance)which offers 50,000 miles after spending $2,500 within 4 months on the Citi Visa...used towards future flights$$.
How much for a /R/T ticket towards meeting that goal. 

Just a couple of thoughts so not to leave $$ on the table.

Have Fun!

Check out what Oz banks are based in Vietnam or are partnered with a Vietnamese bank.

Then open an account with the Oz bank and get a debit card with the $10,000 in that account.

Or look at Oz post offices as they have deals going for travelling people with regards to money.