How many days in advance can I cancel my ED-Visa at immigration before my flight out of Thailand?

@Alex ******

and that you did that and got away with it after you came back and tried to get an extension is great for you

BUT the real way to do it IS

if you are on an extension of stay based on education you should cancel it before you leave the country because just stamping out doesn't cancel it,

AND

many MANY people have had issues returning to thailand, and then trying to get a visa or extension inside the country because they had an uncancelled ED visa extension in their passport