All is possible, but know as mentioned before in the comments that is not easy to find the job. That is the best option, to get employed by Thai company, then they will deal with your visa and rest.
To run your own business/ to open your own company you need 2 mil. Thb capital, and 51% company shares owned by Thai citizen/s. On top of that if you want to employ yourself in your own company by the Thai law, for one foreign employee you need to employ also 4 Thai citizens (good accountant can help with arranging that but that is additional cost: accounting and employees’s taxes and insurance). Also you will need a lawyer to assist with opening the company and add to that work permit cost that is around 60-70k thb if accountant/ agent do it for you… ( if you do it yourself, is cheeper but absolute hell).
All in all everything is doable, but it costs a lot 😏
Other option is elite visa, not really sure but I think is around 1,5 M thb.
It just what they do and always let you pass. No one knows what they want! They want tourists but act like they dont, they dont want people coming for girls but sex tourism is at every corner and in front of every police officer “blind eye” in Bkk in worst form etc for many other examples…..you did nothing wrong, its just how they act… stupid!