My son says you may need to leave the country to cancel your Ed Visa but again he's not 100% sure. Its a pity there is no immigration office in Chiang Rai to ask them there as it can change at different locations. I'm sorry I can't be of more help.
There maybe a fee from the school to cancel your ED visa. I have no experience at all with the Ed Visa so I can't comment on that I'm afraid. Good luck.
My condo always register me. If I create a profile am I able to log in and see my TM30 that was registered by the Condo. Im worried if I create my own account it will duplicate or delete my current TM30.