I just Googled 'condos to rent bangkok' and found several agencies with many places you can choose from. Even some of the tall buildings have apartments on the 4th floor, while others are offices or retail at that level. Your real problem is I understand Thai law does not allow private rentals less that 30 days. You could look on booking.dot com (for example) since they have many AirBnB type properties these days
So can come and go as she pleases right now, for max 3 months each time. The last time she can enter is 12 April 2025 and, if she enters on that date, can stay until 11 July 2025
Elements of Thai culture are indeed feudal and have been surpassed in many western states (although UK still feels feudal in many ways). That's exactly what it is 🤷🏻♂️
Your company needs to be 51% owned by a Thai national, employ a minimum 4 Thai nationals and pay their social security. Then you can get a work permit and non-imm type B visa. But to be successful you need products people will buy. Thailand already has fast food from almost everywhere in the world, and produces some of the world's very best at its own street stalls