Business with my Thai life companion, what visa should i have?

Hello, question is for all the veterans. I am soon to be married to be my Thai girlfriend of 2 years. After our honeymoon I will return to Belgium for 6 months to a year to start my old job. After my return to Thailand we would like to open a business. We already have most the details figured out about our businesconcept. We think Chiang Mai is the place to be for our idea. We have looked into it and would take over an existing business for around 200,000 bath + monthly rent of about 10, 000 baht (the numbers can always fluctuate of course). We would both invest 50/50 with all the documents under my Thai life companions name. To come to my question, which visa would be the least hassle for me in the long term future? A marriage visa with after 1 year renewal, requires 3 months prior extension 400,000 baht on a bank account or proof of 40,000 monthly income, This wont be a problem for me for the first couple of years but eventually i wont have this amount to show on my bank statement, because you never know if a business will be successful or not, What would be the route to take in terms of a visa? I look forward to your suggestions, thank you in advance