Tourism is more than 12% of Thai GDP. How much, one cannot say with any certainty. And a good share of that GDP goes to foreign owners of tourism businesses who hide behind Thai strawmen. That is especially true regarding Chinese tourists.
So we don't know how big a role the arrivals of non-Thais to the Kingdom plays in the real economy. But we do know this - for any country, a 2% or 3% contraction of the economy is an absolute disaster, typically with political consequences.
The HiSo can take it on the chin for a few years, but the 9,000-baht-a-month workers of Thailand cannot take it at all. For any amount of time.
This either results in a political movement threatening the current national order, perhaps leading to the return of martial law. Or the current regime desperately accepting Chinese development projects to stimulate domestic growth, perhaps leading to TH becoming another Chinese protectorate, along the lines of Cambodia and Laos.
It's all bad news for Thai people, and not what they, or anyone else, deserve.