Can I convert my tourist visa to a business visa in 6 weeks, or should I apply for an education visa instead?

Okay, it seems you're just grasping for a long term visa here and this group is NOT for straw grasping :O

Whether you have enough time to register a business and get the required documents comes down to how fast who ever is doing it for you can get it done. SO those are the people you need to be talking to.

AND

the same goes for what ever school you enroll in up in Chiang Mai. Whether they can get the paperwork from the Ministry of Education in the amount of time you have left on your current entry so you can leave the country and get an ED visa is between you and them.

Good Luck, (y)

As I look ahead into 2020, I foresee a Marriage to a Thai if you wish to continue living with your partner in Thailand.

The business visa is a non starter IMHO. The costs associated to set up and employ 4 Thai full time make it difficult to do.

Getting an Ed Visa likely is not possible as you are living in Thailand on back to back visas. Border runs. Extensions etc.

Choose your next steps carefully. Good luck David

What's your nationality? If you're American, it might be worth it to look into contacting the US State Department about opening up the business completely under your name as a treaty of amity business. You'll get full ownership rights (NOT the 49% like most people), and I think it takes about 2 or 3 weeks, or thereabouts.

Just something to keep in mind if you qualify for it.

To many questions and all not visa related to find the answer. If the restaurant is for example owned by your Thais spouse and she has the sole proprietorship she can apply for a work permit for you. If it is not your Thai spouse, you have to sort out another business plan, best is to get a lawyer to advice you to set up the correct business type continue from there. I could be done in 6 weeks but it is quick, you can always go for another border bounce as a new year starts in a few weeks