You're still treatinging this hypothesis as if it were an irrefutable fact.
Dating apps reduce the visibility of sex tourists, as they're no longer going to the gogo bars.
Whether the apps have any effect on the number of tourists is another matter.
Only Pattaya has the apps teeming with cute money boys. App use anywhere else in the world is different. Try finding a selection of cute prostitutes at a fair price on Grindr in your home country.
When did you last travel to the west and try using the apps to find boys?