>that 90 days report thing is completely unrelated to the topic of extending visas, right ?
Yes.
>And it means that every 90 days I have to do that, as long as I am in Thailand ?
To submit it in person, you have a window from 15 days before it's due to 7 days after the due date. To submit it on line, you have a window of 15 days before the due date up to the due date. For mail, contact your local immigration office.
>Can I do it online ? If so, where and what to know ?
Free. Not submitting the 90 day report will result in a fine of 2K THB the next time you attempt to acquire an extension of stay.
>I will reach the 90th day of stay on Wednesday 9th of March, meaning it has to be completed on Tuesday 8th max ?
It has to be completed by Wednesday 9th of March.
However, if this is your first extension of stay, you should have received a small slip in your passport that looks like that attached. What extension of stay did you acquire? If you got a 60 day extension of stay based on unable to travel due to COVID-19, did you ask the 90 day reporting desk what the policy is?
>Nothing is mentioned about having Thai bank account with 400,000 which everyone mentions?
That is for the extension of stay, not the visa. However, some consulates do want to see 400K THB in local currency before issuing the visa (and other's don't, like Savannakhet).
You will request an Extension of Stay Based on Unable to Travel due to Medical Reasons from the hospital that is overseeing your quarantine. Some public hospitals are extremely difficult to acquire this extension of stay from.
The cost is 1,900 THB. The hospital can submit the paperwork on your behalf.
>meaning the employers letter must be address to .
The employer must write a letter to the consulate asking for the Non-B visa to be issued. Different consulates have slightly different requirements.
>And the requirements in getting back?
You will need a Thai pass, approved health insurance valid for 89 days (the length of the entry stamp from the Non-B visa), and booking at a test-n-go center.