@Amanda **********
I have seen people leave the country (stamping out on a current extension based on employment) come back into the country on a valid tourist visa they got from a thai consulate, and then when they went for the extension on the tourist visa the officer noticed they never canceled their extension, and fined them 500baht a day for overstaying on the extension based on employment even though they had exited the country and came back on on a valid tourist visa
Be prepared to be fined from the date you stopped working, until you cancel your extension of stay. It maxes out at 20K baht or 40 days at 500baht a day.