thinking as a thai junta member: if you want to stay here, and work here, please be kind enough as to pay 40% of your wage in taxes rather than spend 5% on fried rice.
As a short term tourist, you're a valuable resource. As a long term resident, you may very quickly become a net drain if you pay your tax somewhere else.
And for most people, if they live and work in Thailand most of the time, they will either not pay tax in their home country, or will pay tax proportional to the amount of time they live there, on the expectation that someone who is resident outside the country most of the time will not expend much local resources.
Laws have dealt with this kind of scenario for a very long time since it's been an issue in border areas pretty much "forever" that people try all kinds of creative methods to cut their tax costs. There's nothing particularly new here with the internet other than magnitude.
The biggest notable exception that can cause expensive double taxation is the US, since the IRS likes to get their hands on US citizens income regardless where they live, but even in that case it's ameliorated substantially for most countries via double taxation treaties.
The tax argument only holds water if your income is earned in the country you are living in. That money came from a system that is supported by government and shared infrastructure and services. So yes, there is a strong legal and economic argument saying if you earn money from Thailand you should pay taxes in Thailand. The key here being earning money in/from Thailand.
But if you are visiting Thailand, but earning money in the US and paying taxes in the US, it's pretty difficult to say that you are a net drain.
You absolutely are equivalent economically to a tourist as far as your impact on the economy is concerned. As a non-local citizen, you won't have access to state health care (if it's provided) or anything else tax paying citizens have access to. And your absence from the country would be a net negative value since you will be paying $0 into the local economy instead of room and board, internet connectivity, and general consumption, which all can be taxed with a VAT.
Edit: Also, I promise I'm not trying to be an internet jerk :). But I'm not sure what you mean by laws have had to deal with this exact scenario for a long time.
They haven't.
Generally speaking, the common case is for people to evade taxes by leaving where you earn money and claiming to be a citizen of some other country with more lenient tax laws. Which is the total inverse of this scenario.
The U.S. and China both offer an expatriate exemption (first $100k in income for the US) and foreign tax credits against U.S./China taxes for local country income taxes paid.
If you spend $5 a day while earning $5000 a month, it's better to have one person who really loves the country and wants to stay paying income taxes, rather than 100 staying and paying VAT.
The typical government member in my experience tends to think in terms of "people will just pay more" rather than "they will go somewhere else".
EDIT: Moreover: how should a government discriminate? If you are working for a company in Norway you are probably earning better than someone working for a company in laos. If both of you are residing in vietnam, should I expect the latter to spend more in VAT than 50% of the vietnamese college graduates ?
That's a pretty stupid viewpoint in this context, considering I've already demonstrated my willingness to leave and go somewhere cheaper (Canada -> Vietnam). You'd think they'd rather have something from me than nothing.
In the Netherlands, for example, >50% of income tax is received from the 10% highest earners. So it's not unreasonable to expect a high earner to contribute accordingly.
EDIT: Heavy downvoting, but this is how things are in most Western democracies, like it or not.