Arrival tax? Wait for a (government) departure tax...
"Departure tax proposed
Thais and foreign residents would pay 1,000 baht to leave the country via air under surprise levy (...)
The (Revenue) department posted the public hearing questionnaire on its website (...)
(...) in an attempt to prevent locals from spending excessively abroad (...)"
(Source: BP, 6th May, 2023.
Links to BP articles aren't allowed here, and I wasn't like typing the whole text here. Who's interested can visit the source online.)
To comment on this, if I had to pay this levy every time I left the country, I'd spend even more abroad on things that are cheaper there than in Thailand, just to compensate for this extra tax, meaning 1,000 baht more for Thailand's revenue department, but thousands less spent in Thailand, but instead abroad.