Starting a local company as an expat - what visa do I require

I plan to start a Thai company in the property/visa fields - acting as a broker or agent. I am entitled to a Retirement, Non-Immigrant Visa or even a Marraige Visa. My question is whether such a company can be held in the name of an expat or must there be Thai share holding? If so, what is the percentage shareholding required by law. Should there be Thai shareholding required, how can this be expected if there are no willing Thai partners willing to invest in the fledgling business? Thank you, farangafrique