@Mason ******
What should I tell the Thai Embassy in London?
I have nothing to do with Thai Embassy in Londen, I am not from UK.
You applied for softpower and they asked you these documents?
Nothing wrong with it because you clearly don't know about the rules of working in Thailand.
But London Embassy is not the authority to decide if you can work in Thailand.
They just decide what kind of proof they want for visa.
When they ask something thad does not mean it is a requirement for all embassies.
Look how they often ask for a real flight ticket while other embassies just accept flight number of the intended flight.
So the fact they ask you to sign a document is not proof that they allow you to work online in Thailand.