Are you teaching any people inside Thailand? If so then you can not get this new visa, as that is one of the restrictions. If all of the people you teach remote, and not in Thailand, then you might, as long as the company you work for is legal, and will write you an employment confirmation letter, and that you have the 500,000 baht that is also required in your personal bank account, and, you can only apply for it out of Thailand, at most embassies, and consulates now. Just remember to look at the particular one you plan to go to, as many require an appointment now, and with some the queue can be weeks away.
then you will be okay, as long as they will issue you a signed letter saying you work for them, and a bank statement showing that you have the equivalent of at least 500,000 baht in your personal bank account.
If you are doing any of your work inside Thailand then this visa does not apply to you. It is only for work done remotely outside of Thailand while you stay in Thailand. That is what I understand you by saying semi remote work.
Vientiane embassy requires an appointment for everything, and there might not be any slots left for this month. Make absolutely sure you make an appointment there first before you end your current stamp.
to answer your question of why those countries refuse is that Thailand now requires them to certify that the monthly income is true, and they don't do that, and never have. All those countries ever did was notarize your signature on a document stating your monthly income. They did not, and would not, verify if what you said on the document was true. They only notarized your signature that you personally signed the document. Thailand no longer allows that, because too many people lie.