Do I need a work permit to teach online to European students while living in Thailand?

You are teaching online to students in Europe or Europeans in Thailand. If the latter, work permit etc

Are you going to work for yourself, not a platform? Where will your payments go?

Mine go to my home country and I travel as a tourist and I do my own thing- using a good VPN, and not through a platform. Yours is a bit more complicated as you may face more scrutiny because you’re a foreign resident, but possibly covered somewhat due to marriage? 🤔

It’s a curious position.

I work in international schools sometimes and this shows income (legally, obviously) either in country or from a recent country, so I’ve never had a problem showing that I can support myself. Or have savings.

Having been there so long- do you maintain any banking in your home country?

I lived in Vietnam and I know that banking is extremely monitored in some countries… conundrum.

I'm puzzled, you've been living & working in Thailand for twenty years and you need advice on visas 🤔 hmm!

Are you married thai citizen?

You would at the very least need to be registered as self employed somewhere outside Thailand, your income would have to be reported and pay tax there. Thailand has no concept of self employment as far as I'm aware and in any case that would rule out the dtv

You can be self-employed and get the DTV, the problem in your case is that you need to show evidence of that and while it may vary between embassies/consulates, things like tax returns, previous evidence of payments and contracts can/are asked for as evidence.

Assuming you have the money and the patience, it seems like DTV is an excellent fit for you. Create a company in the EU (your home country, or Estonia), "season" it, and Somchai's your uncle. Someone else with a WP cancelled it to get DTV.

Of course you'll be losing your shot at permanent residency or citizenship, but I guess you know that and don't mind.

You are working for a non Thai online school?

You should be a doorman.