Why not have your partner home-school your 13 year old and mentor you son into your existing business? I'd be mentoring my partner into the business as well. The best employment prospects for westerners in Thailand is going to be some type of remote or digital nomad type of work.
I'm not sure what you are asking either, You're generally allowed to stay for up to 60 days visa free, per visit. A short-term tourist visa is generally only good for a single entry.