That's no surprise and although many claim in Asian countries you can work remotely or have income and don't need to report or pay tax, in 99.9pct of the cases you remain under the radar and they will leave you alone, which doesn't mean you are operating according the law.
Mostly you get caught by something unforeseen (I speak out of experience) , and once you are in their eye sight, neither the law nor the authorities are at your side as you are breaking the law, since doing any work or business on a tourist visa is not allowed. The outcome depends on their︀ goal and your connections, in the best case scenario they teach you a lesson and︁ you can agree on the "fine", worst case scenario you have to pay the taxes︂ and fines they claim, get blacklisted for a period and deported.
Most people I know︃ in SEA do business and operate even multiple companies on a tourist visa, they don't︄ encounter any issues. Only when someone reports you or you have bad luck, well then︅ you have bad luck and belong to the 0.1pct.
The longer you stay in a︆ country working illegally, the higher the risk. Just as with a business where you have︇ after 5years a higher risk of a tax audit, it's recommended after 3-5 years to︈ move to another country for some period.
