The consensus in this group is you will be required to every 6 months prove to immigration that you have been learning whatever it is you got your DTV for.
If you got it for cooking classes then they will expect you to cook some Thai food while they watch and taste it.
If you have been doing Thai boxing you will have to show some Thai boxing skills.
You were not doing anything illegal or against the rules on your ED visa.
People can be in Thailand on a visa exempt stamp and do their remote computer work and it's not illegal. You don't have to be on a DTV to be able to do remote work.
But if you have been working in Thailand for a Thai business and you didn't have a work permit then there is a problem