Am I overstayed in Thailand after my employer canceled my work permit without informing me?

@Ahsan *******

I outlined what you can do

LEAVE NOW, stamping out on your current extension like nothing is the matter, go to a thai consulate get a single entry tourist visa come back in get stamped in for 60 days

THEN if you do find another job and when you go to get a new Non-B you deal with the fact you did things "out of sequence" and you pay the 20K baht max fine to clear it up at the immigration office before you can get either a Non-B visa or an extension from inside the country

OR

You take the termination paperwork and the proof your work permit was cancelled to the immigration office, cancel the extension, pay the overstay, get the stamp in your passport and then leave.

you don't have any other options. Those are the only two

IF you take the receipt of the work permit being cancelled to the immigration office with your termination paperwork your extension will be cancelled the day the work permit was. SO you would be on overstay since then. You would get 500 baht a day fine and you would get an overstay stamp in your passport.

IF you exit the country stamping out and then returning on a tourist visa you will have problems when you go to get a new Non-B but you will have avoided an overstay stamp.