There is paper work. You need a TM30, some copies of relevant pages of the passport, and fill out the extension form and have a passport photo of yours, or two. Just like ever extension.
All visa extensions (end visa excepts) are: 1900THB. Makes no sense to change that for a particular visa, when the owner can just bounce out and back in.
Because I know it is easy. And you don't. E.g. married, requirement for four workers, drops to two, and on request: it drops to one, which is your spouse. So ... plenty of international cooks in their own kitchen: all over Isaan.
Obviously sooner or later they higher some waiters ...
As I said: your half knowledge is completely irrelevant, as the husband does not plan to work as cook, as he is disabled.
Up to 5M registered capital no obligation to pay anything into the company. For bigger companies, it is a percentage. But unless you plan to run a shop selling sports cars or yachts, it barely makes sense for a foreigner - oops - alien.
Yes, and? I know plenty foreign cousin restaurants where a foreigner is chef or cook. You are trying to argue about something that is not relevant for anyone here.