Can I convert my 30-day Thai pass to a work permit for business?

You didn't come on a 30 day Thailand Pass. Thailand Passes are not visas and don't allow any particular length of stay. They are just a government approval of your entry documents to ensure you have the proper hotel booking, covid test bookings, insurance, etc. You still need whatever visa you needed to enter, or you likely entered on a 30 day visa exempt entry. The stamp in your passport is what shows your allowed stay-till date, not any length of time you originally put when you applied for Thailand Pass as your estimated stay length. If you go around asking about converting a Thailand Pass to a work permit, no one will understand what you are talking about. You need a Non-B visa and a work permit, not just a work permit. Work permits are issued by the Ministry of Labor, NOT by immigration so going there won't do a thing for you. And work permits are applied for by the employer, not by yourself. Both the Non-B visa application and work permit application process takes many steps with many documents and photos required. Here's the list for the Non-B:

I would get the covid extension tmrow and then talk to an agent and try to figure something out. Or just buy an Elite Visa and be done with it.

Growing a business with a friend? You'd need a Non-B visa and you'd have to apply for a work permit. Your position cannot be a prohibited profession and the company needs to employ 4 thais for every 1 foreigner.