Just muling at this stage to see if I can achieve the following. Please feel welcome to narrow my focus to the correct requirements.

I am married to a thai citizen, am a tad over 50 years, am a 95+% graduate of Healthy Buffalo University, and see an opportunity that could go close to creating sufficent cashflow in Thailand to meet say the ฿800,000 per annum married over 50 requirement.

Can I come into Thailand on a visa, and what visa, and be a 1/4 share bussiness partner - the other three equal share partners would be my thai wife and family, who would like her and grand daughter back home to spoil them? Are there any other charges over the top of the "over 50 married to a thai" visa requirement to entering a family bussiness that I have to pay under thai legislation?

And I think I recall from previous threads that the ฿800k can be jointly earnt by a married couple in Thailand, prove being a joint thai bank A/C? Also the account can go below the ฿800k during the year but has to be at that value when yearly visa renewal is sought?

The 800,000 has to be in your name only. You can spend it or some of it and top it up next year.

Others will comment on business