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
It happened to me on Friday but it wasn't the bank account they questioned me about. They looked up my DTV and saw I got it for Thai boxing. He didn't believe I was doing boxing cause I weigh 160kg, I'm super overweight and unfit.
They laughed at me and then told me to shadow box for 5 minutes to prove I'm passionate about boxing.