I have been dozens of times through immigration, I was never asked for this. When you check the Thai consulate websites in your home country... A lot of info about visa. But this money is never mentioned. If immigration asks, it is just an excuse to throw you out. That is my understanding. I am sure that 99% of tourists who arrive do not have this money in cash. I never carry that much in cash myself.
If they ask you to show this it means that they already decided to refuse you. They are just looking for an easy reason to fill in on their documents. If it is your first time to Thailand they will not ask you for this.
If he doesn't need money from his business to live it will make things different. "100 business ideas" Maybe you can share some? I started my business with less. But I did not have to pay to officially start a business in Thailand.
I have my own business. I started one and failed, I started another one that failed too. Now I have a nice business making enough money. But I would not be able to handle the pressure of having to start here from 0 with only 200k Baht and 4 people depending on me.
. Even a McDonalds on SUKHUMVIT closed because there are no people spending money. They say that tourism is only 20%. But these are official figures, it is a lot more. It means that people working in tourism stopped spending money. And the families depending on that stopped spending money. That is a -20%+ effect on everything. That is a lot. Take a car and drive around in Pattaya. The main streets are ok, but in all sois connected the blinds are down everywhere. It even looks scary. Since Covid I see people sleeping on my street in Bangkok, never saw that before.