what are you talking about? I have a very good long term visa extension, with no money in the bank requirements and have never done any border run, ever. I'm in and out of immigration in less than 3 hours once a year, and I can legally work in Thailand. You, on the DTV visa must leave the country, and return, at least every 360 days, if you get the one time a year extension, and that takes much more time than a few hours it takes me to extend my stay here every year. I haven't been out of Thailand in 8 years....lolol. try again in your negative inferences.
Be fully aware that you will need a work permit to teach, and the main requirement, besides already having a job offer, is that you have a university degree. It can be in any subject,, but it is required, and it must be certified as being real, so you can't buy one anymore on khaosan road.
depending on the type of business you might be able to set-up under the BOI, board of investment, that can give you full ownership, and no required Thai employees. If you are American setting up under the Treaty of Amity is an option, but only if you are American. Stock voting rights is also a way to protect your ownership.
The basic financials on opening a business, and specifically in qualifying for a work permit, is that you have at least bt2million in registered capital in the business, together with hiring at least 4 Thai employees you pay wages and social security on. There are business structures that can be used to bypass the Thai employees, and the ownership requirement, but not the bt2million in registered capital for the work permit. Also be aware that the corporation must make a profit within 3
You might try comparing the cost of staying in Thailand, doing border runs, and extensions, compared to your interest loss. It is pretty close to the same when you consider all costs trying to stay here as a tourist, or on any other visa.
You have a lot more to consider, given what you want to do, than simply the visa. First get a type O visa based on Thai wife. This has two advantages, first being you can work with this visa, and get a work permit, but that is not the main reason in your case. The main reason to get that visa is going to be the actual cost of you doing business, and the requirements to get your work permit, that you can not do any work without, not even volunteering. For a regular business you can only own 49% of it. The rest must be owned by Thais. The next things, and this is where being on a marriage visa comes into play, you must have bt2million in registered capital in the business, and hire at least 4 Thai employees you pay wages and social security on in order to get your work permit. If you set the business up with your Thai wife those amounts are cut in half, bt1million in registered capital, and only hiring two Thai employees to get your work permit. There are other business structures you can set up under, but any other business structure with require the bt2million in registered capital for your work permit. I might add that one of the Thai workers can be your accountant, as accounting is a restricted occupation for Thais only, and you must have a licensed Thai accountant. If you are working purely remotely, with no business of any kind done in Thailand then you have another option, but that doesn't sound like your intention. For the visa itself you will need bt400,000+ in your bank account, together with your marriage license, a copy of your wife's ID card, and a copy of the house book she is listed in, she will know all about this part. Also copies of your passport. These will get you your 90 day marriage visa before you enter Thailand from the Thai embassy/consulate you apply through. Once you get to Thailand you get a Thai bank account in your name only, and transfer the bt400,000 into that account. You go to immigration, with your wife, and get the list of documents needed for your one year visa extension. When you have all these documents, and it is nothing difficult to get, it just takes time. When your bt400,000+ has been in your Thai bank account for two months then, together with all the documents, you can apply for your one year extension. Remember though, when ever you are dealing with immigration concerning this visa, and extension always take your wife with you. Keep copies of all the documents, as the following years all you need is updated bank letters, and new pictures. Everything else is the same, unless you moved.
Understand that this is a brand new visa, and most banks aren't even aware of it yet. When they are not sure they will say no. It is classed as a tourist visa as far as they are concerned, and that is a no. If you want to make it to the bank's advantage to give you an account then make arrangements to immediately transfer your bt500,000 equivalent by SWIFT transfer as soon as they give you the account, and in their presence. Remember, it doesn't matter what country the bank is in. A bank manager would be much more inclined to open an account for you when you can put bt500,000 into it immediately rather than the bt500 minimum to open it. If you make it worthwhile they will open the account, and not with promises, but with immediate cash transfer into the account.