What type of visa should I apply for if I want to obtain a work permit while on a marriage visa in Thailand?

You are overlooking one very important detail about getting a work permit. For a company, even your own, to sponsor your work permit they must have at least bt2million in registered capital, and hire, and pay, at least 4 Thai employees. For a regular business setup there are no exceptions to this. If it is a business setup with your wife, and you are on a marriage visa extension then these requirements are cut in half, to bt1million in registered capital, and just 2 Thai employees you pay wages and social security on. The age of proxy workers ended this year. If you no longer have the bt400,000 for your marriage visa extension I doubt if your company has the required amount of registered capital for a work permit. The cheapest option would be to borrow the bt400,000 for the three months you would need it, as there is no requirement as to where that money came from. Only that it is in your account for at least two months before you apply, and in some provinces for the under consideration time period before you get your yearly stamp. If your wife's family can't loan you the money, then your wife will know a loan shark that can. It is not that expensive to do.

you used extension, not visa ☑️, better go back to your country.

Marriage visa is completely oki for a work permit. And you only need two Thai workers unlike other visas, if you are married. And, "Worker" means you only have to pay social insurance for them, they do not really need to work or receive a wage (no contract required either). So employ your wife, one of the kids or the mother of your wife: unless you need a real worker anyway.

You don't need another visa.

@Jens ********

I think what you want to tell us, that you don't have 400.000.- THB in your Thai bank account, in order to apply for another 1-year extension of stay based on being married to a Thai. This makes me wonder how you achieved this extension based on marriage in the recent year. I assume you got it in Savannakhet, where until last year you weren't required to show financials at all. You had one year of time to accumulate 400.000 THB in savings so you can continue getting the "1-year extension based on being married to a Thai wife" . . . . . You said you have a company. Is this company inside Thailand or is it outside of Thailand? In case it is outside of Thailand, does this company not earn you enough to put aside 400.000.- THB ? You do have only limited options

A marriage visa/extension is a work allowable visa, so you don't need to change your extension at all. You just need the company to submit the documentation for the work permit.

If you are still on a marriage extension of stay you don't need a new Visa just a work permit using the documentation your company will provide