Resubmit proof of remote work? What would be the point of this, the document is exactly the same provided when apply for dtv. I have it in my email, but how can they ask that at the airport when you arrive? You already have the visa. You think they just say oh, go back to your home country to get the documents, sorry nobody told you about this, bye now take care?
Take both passports with you, on dtv it has passport number its issued on. Later when you arrive, go to immigration/embassy (cant remember which) to update the passport number on your visa
If you dont have a company registered anywhere, I think they consider you work here in Thailand and for DTV, thats prohibited. Register a company and pay taxes, then apply again...