The Netherlands and Thailand are in the process of signing of a new tax treaty where its clearly stated that source principle is in effect. where the money is earned, the tax is also paid
Most people will never pay. I not say it never happens. And not all treaties are the same. Some are very clear to which country does the total taxation.
The IO did confuse the old visa on arrival for indians with the new visa exempt for Indians. Under visa on arrival there is no 30 days extension possible. Under visa exempt its a standard option. Also for Indians
Being a tax resident does not mean you have to pay tax. Many countries have a double tax treaty with Thailand. Most especialy retired persons will never pay any taxes here.