I am here on a non-immigration type O 12 month visa which has expired and I'm on my last 90 days extension

I am going to move to a Ed Visa but was told I need to cancel the non-imm visa and then leave the country, get the Ed Visa and come back on the Ed Visa.

Is this correct? Do I still have to cancel the non-imm even though it has expired (but I am still here on it)?

I will be leaving the country soon any way and will probably be coming back on the standard 30 days. After that I plan to leave to go somewhere where I can get the Ed Visa.

Any advice?

You do not need to cancel anything. Just go abroad and apply for an ED-visa, with all relevant paperwork.

Thanks, is that because it has expired or do you not need to cancel it even if it was still valid?

It is still valid, but when you apply for a new visa it automatically becomes invalid.

Only an extension would require (but it appears you are on a 90 day entry rather than a one year extension of stay from Immigration), which is beyond the validity of your visa so that ends immediately when you depart Thailand.

Thanks. I'm leaving Thailand for a few days, then expect I will come back in on a standard 30 day then I will get the paper work for the Ed Visa and then go to somewhere local (Sing, Malay, etc) and get the Ed Visa then come back into Thailand on the new visa. Simples.