No health insurance requirement, you're probably looking at the non-imm O-A visa requirements. No income requirement either, if you deposit 800K in a Thai bank.
What you need is a non-imm O single entry visa from a Thai embassy/consulate. Then you open a bank account, put the funds in it and apply for a one-year extension of stay inside Thailand.
Of course you can be successful as a biz owner, that's what I did. His documents were not OK. A nasty mention on the extract of business register, even if it's a standard one. Plus he provided only the translation, not the original document. Translations, whether official or done on your own, always accompany the original document.
It's his own biz. He provided, in a second attempt after having provided somewhat unrelated docs, an extract of the business register which has a nasty, although standard mention ("this document has no legal value"). OP has been doing everything a bit light-heartedly, I suppose. His translations were definitely off as well. Provided the translations only (probably using Google Translate with lens), not the original documents.
Some of the facts are not in posts, the applicant told me in a DM. I expected the mention "this document has no legal value" to be an issue. He did not blink an eye and sent the doc without an explanation. An easy way around it would have been to provide the link to the English language website of the business register in the cover letter, together with a short explanation of how to check the authenticity of the data submitted.
If they do, they won't accept everybody I guess. I think it's a nice perk if they really refund everything. Unless their business model is to systematically deny refunds on the basis of inaccurate data provided by the applicant.
The OP actually knows where their application was weak. Provided "uncredible employment documents" 🫠. This remark was on their soon-to-be-canceled visa too. OP first sent documents which were not adequate. After a request for further documents, OP added documents which contained the disclaimer: "this document has no legal value" and no other document/explanation. The document was actually OK, but this mention is standard and it definitely made a bad impression. OP should have sent another one, or at least provide clarification.