You can likely pay a local agent to do a 30 day tourist extension, 1 time, you may be able to avoid an actual trip in.
For anything past that 30 days.
In all cases, without a local diagnosis from a hospital/doctor and a document explaining the reason you cannot fly, you will not get an emergency medical extension.
You will need a local agent and a fistful of money, to find a possible workaround.
You may DM me if you like and I will walk you through possible options.
BUT you cannot use income, period.
You will need to use banked funds for whatever your initial visa will be.
However you can also see if the US embassy will still allow a non-o 90 day based on retirement AND a dependant 90 day non-o based on visiting non Thai family.
This way you would only need 800k total for 2 of you.
The US and CANADIAN embassies have allowed this, I don't know about 2025 however.