@Leong **********
Just because the school offers online classes does not mean it's legal for ED visa purposes. The reason ED visa exists at all is because you are stating that you need a visa to be in Thailand to attend a class IN PERSON. If you are attending an online class you do not need to be in Thailand, and therefore you do not need a visa. The visa is not because you want to be in Thailand, it's because the ONLY WAY you can attend the class is to be there in person. Online classes do not qualify for an ED visa.