Is my Non-B visa still valid if I haven't done a border run due to closed borders?

That visa is good for unlimited entries during the validity of the visa itself and every entry gets you stamped in for 90 days.

However due to the inability to 'bounce out and back' to get a new 90 day stamp everyone on those types of visas (year-mulit-Non-Imm) have been stuck and on amnesty.

IF the borders open back up by the time amnesty runs out (Sept 26th) you could bounce out and back to get a new 90 day entry on the still valid visa.

However if they haven't opened up, you need to either get a long term extension of stay based on employment OR prepare to leave the country when amnesty ends.

There is no need to apply for a new VISA (because your current one is valid until March 2021), it's just what will happen to you when this current amnesty runs out that's the question

okay, let's get the work permit out of the equation because this is the thai VISA advice group :P

I take it you have a year-long, multi-entry Non-B VISA that you got at a thai consulate in another country and you most likely entered the country the last time in March and got a 90 day entry stamp and then went on amnesty?

Is that correct?