The passive income approach works only if you're from a country whose embassy will certify your income. US and UK, for example, stopped doing so years ago.
On every Thai Embassy website, there’s a list of jobs reserved for Thais. Start there. If all of the jobs you’re qualified to do are on that list, it may be difficult for you to work in Thailand.
The ask:thailand community, consisting of multiple Q/A groups with over 100,000 members, powers this platform. It is not an official government resource. Our members actively contribute to this resource, and while we strive for accuracy, we cannot guarantee its complete reliability. Assistance to travelers is provided as a community service.