CONDOMINIUMS
Purchasing a condominium is the easiest way to own property in Thailand as you can purchase in your own name without having the hassle of nominees. Foreigners are permitted under Thai law to own up to 49% of the units in any condominium block. In order to transfer any monies used to purchase a condominium back out of the country at a later date you will need proof from the bank that the monies were used for this purpose so you will need to get either a Tor Tor 3 form or a payment slip from the bank as supporting proof.

Tor Tor 3 (TT3) and payment slips explained.
A Tor Tor 3 (TT3) is actually now called a Foreign currency transfer form. This form is only necessary if you transfer over 20,000 USD into Thailand in any foreign currency to buy a property and at a later date you wish to sell the property and transfer the money back out of the country. For any other payment method you will need to collect a payment slip if you want to transfer money back out of the country.
The following lists the scenarios for obtaining a TT3 form or payment slip:

If you transfer a foreign currency amount greater than 20,000 USD to Thailand straight into the developer’s bank account, then the developer can get the TT3 form from the bank for you.

If you transfer a foreign currency amount less than 20,000 USD to Thailand straight into the developer’s bank account then the developer can get a payment slip from the bank for you as support documentation (instead of a TT3 form).

If you transfer a foreign currency amount greater than 20,000 USD into a bank account you hold in Thailand and subsequently transfer that money to the developer’s bank account in Thailand then you are responsible for getting the TT3 form from your bank.

For all other methods of payment, you will need to get a payment slip from the bank for support documentation (instead of a TT3 form).

Please note that if you have transferred money into Thailand over 10 years ago and did not get a TT3 or payment slip then unfortunately as the banks don’t hold records that long, then there is no way the bank can provide you with a TT3 or payment slip.