What documents do I need to cancel my ED visa and how long will I have to stay in Thailand afterwards?

To cancel your ED visa, you primarily need the school's certificate letter, though it's advisable to confirm with immigration for any additional document requirements. After cancellation, you will typically enter a grace period (amnesty) providing you until 11:59 PM on the specified date to leave Thailand, or you will have until that time on the same day if you cancel your extension later.