Do I need to cancel my ED visa at an immigration office before doing a border run, and what is the time frame I have to leave the country once canceled?

Most people who cancel ED visa extensions take a paper from the school saying they are stopping studying on xxx date and go to the immigration office a week or so BEFORE that date to get the extension canceled and get a new stamp that lets you stay until that date on the termination of study paperwork. Then you can just leave on or before that date

A FEW immigration offices won't let you do this, so depending on where you are and what office you use, you might have to cancel the extension and immediately leave the country. OR cancel the extension and then get a 7 day extension denied stamp that gives you a week to get outta thailand.

and you are on an EXTENSION from the immigration office right, and not just the first 90 days from the ED visa?