What a silly headline. The Thai law says the equivalent of Bht 20,000 in a convertible currency, cash, actual bank notes. So today Bht 20k is $557 not $417, or GBP 440 would do, or EUR 515.
No good saying you have an ATM card, there are no machines until after Immigration at Suvanabhumi or Don Muang. Don't know about Phuket or Chiang Mai but would suspect the same. Showing a bank app is not sufficient.
In 22 years coming & going I have never been asked, must be my kind face, but they could use it as a reason if they don't like you or suspect your intentions.