@Benjamin *****
yes, I've spoken to both places, but they each only know about going to one. E.g. Duke says yes you can get an ED visa to study here, mahidol says the same, but the switch between the two is unclear.
I must have gotten the 1 year maximum for Ed visa from the language school requirements. It makes sense that I can continue at Mahidol until my program concludes.
I contacted the embassy here in Australia but they weren't sure and told me to contact immigration in Thailand. I've been trying to get into contact with immigration but can't seem to get through. The website only shows info about changing visa types e.g. Tourist to Ed. I tried calling the hotline +66 1178, but it says the number is invalid.