@Karmaa ******
Proof of funds when entering Thailand
Basically, immigration only asks people who got an extensive travel history to Thailand stamped in their passport and who have taken advantage of the visa exemption in quick succession, for a proof of cash.
A border official will start asking if he suspects visa misuse – a misuse of the visa-exempt entry for a long-term stay. It means they will only start asking for the “famous 3 proofs” if they are looking for a reason to deny entry.
The criteria according to which immigration at the border decides on an entry permit are listed in the so-called "Section 12" of the Thai immigration police. This can be found by googling "Section 12 Thailand".
In addition, an immigration officer has individual freedom of decision. The presence of a visa does NOT entitle you to entry if the officer is of the opinion that you are violating an article of "Section 12", or have been “misusing” touristic entries for a long term stay in Thailand.
The fact that many people claim that the have never been asked for proof of funds, does NOT mean that you got a guarantee that you won’t or can’t be asked.
Proof of cash is one of three instruments that immigration uses as a reason to refuse entry.
They ask people for the THREE famous proofs, which you ARE REQUIRED TO HAVE ON YOU, as per see this is a law!
***20,000 THB in cash (accepted as well in another currency, but NOT accepted in form of a credit card or bank statements),
*** proof of booked accommodation for the next few nights
*** proof of onward travel out of Thailand within the 60 days that you get stamped with when entering without a visa.
"Real" tourists are generally not asked for the three proofs!
If you are actually asked for cash, it is better to have the approximately 650 Euros/$700 USD with you. Because inside the area before Immigration counters of the BKK Suvarnabhumi Airport, there are no ATMs where you could withdraw cash.
Unconfirmed reports are that there is an ATM in the space where citizens of some countries buy the “visa-on-arrival”.