How many days must be left on my visa before applying for an ED visa in Thailand?

It takes 2 months for turn around. When I came here on exempt i started it my first week and it came back a week before my exempt stamp would expire ( didnt extend )

School will send off acceptance letter and request to the ministry of education for permission to study.

If accepted you will then goto immigration at index mall with paperwork to be placed under consideration ( process time to grt visa ) you will be given a date to return to immigration by the airport ( main office ) where you will get your 3 month stamp

That you extend for another 3 months for 1900 baht will do this 3 times and still do 90 day report ( based off your education visa stamp )

Because it's a conversion and you'll receive an under consideration stamp, you likely need 14-21 days (depending on immigration office) left on your stamp in order to apply to convert to ED from tourist entry.