@Milad ********
then you won’t get the visa…
It doesn’t have to be Muay Thai, there are other ‘soft power’ options.
The point is you won’t get the DTV based on your rental income, without a company and employment contract etc etc.
As you’ve been advised applying for the DTV via the soft power route is the option for you.
Thailand also has a ‘golden visa’ equivalent: Google Thailand privilege visa. Good luck