I think this visa just is not suitable for you, Thailand wants to attract people with enough easy accesible money which can be spend, and you don't like money on banks.
The staff of the consulaten does not need to know about trading, just as they do not need about all kind of other jobs.
They only need to see proof of your job, which simply is contract as employee from a foreign company which status your function can be done remote, or in case you are freelancer, they need to see contracts with your clients.
When you only trade for yourself and not as employee of a company or as freelancer for clients, I understand why they not approve your application since you do not comply with the requirements, but you don't seem to understand that.
Register a company, write a contract to hire yourself as employee and your chances are a lot better.
You either do the trading as employee of a company, or trade for clients.
In both cases there should be a contract.
Just trading for yourself is not really make you a remote worker or digital nomad.
No doubt you can make money this way, but it is also easy to lose money, so I can understand embassy does not see your investment portfolio as proof of being digital nomad or remote worker.
that does not surprise me, because a lot of traders/speculants only trade for their own portfolio, and don't have clients. That is of course not really a remote job.
I understand agents can help, but topicstarter has problems with financial requirement of 500k and that is nothing any agent can arrange outside Thailand