Seek a professional insurance agent or broker. Sure they make money from their jobs, but not using one will not lower your premium (you will not pay a higher premium for using one).
Word of caution: the odds will be stacked against you if anything does go wrong in someone’s hometown, no matter how well you’ve set it up to protect yourself legally.
Best advice is to consult a lawyer to know the ins and outs of business and to protect yourself. Structure as if you would with anyone else you don’t have an intimate relationship with. One horror story I’ve recently seen/heard: business bought, completely renovated at great expense, and the landlord refused to renew the one-year lease (a bad assumption that it was renewable). Business owner lost everything. Doing business with a significant other, I won’t comment on. Those pitfalls are human, not country-specific, but still worth thinking about and protecting yourself accordingly.
That’s why I said visa or exempt. It’s not as unclear as the squint-eyed, constipated old biddies on here who like to criticize make it out to be. They should go back to their knitting and prune juice.
It’s pretty clear to me. How to enter (Visa or exempt) and timing for visits to other countries and lengths of stay there or border runs to get more time back in Thailand. What’s so difficult about the post? I don’t know the answer, but I’ve seen lots of advice on the subject before.
The same human things can happen in any kind of partnership in any country. Behaviors don’t change from country to country. The only difference is the laws that govern them. Get legal advice to know those differences and structure your business partnership to protect yourself. But even this is not always sufficient protection in places that are traditionally corrupt and/or have an unfavorable bias toward foreigners.