I teach students from my home country so it's totally irrelevant to Thailand. But on the DTV application, I chose "Unemployed + No income". Technically it's a lie but that's what I read people did and should do on this group so that they don't require further documents related to your job.
I'm also a self-employed English teacher but chose to go Soft Power route because there are just fewer documents to provide. I think you should make sure you have all the required documents b4 you choose to go down that path. If not, just go Soft Power and pay for a 6-month course minimum.
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