How can I prove my inheritance for the DTV visa application?

I’m applying for the DTV

I already uploaded 6 months of bank statements from my savings account showing a stable balance of over £13,500 GBP (well above the 500,000 THB requirement).

This money is from an inheritance, but I’m not sure how to prove that in a way they will accept.

Questions:

1️⃣ Do I need to write a separate letter specifically explaining the inheritance, even though I mentioned it briefly in my original cover letter?

2️⃣ Do I need to show the original deposit transaction from when the inheritance was paid in, or is the 6-month stability enough?

If anyone else has used inheritance funds for their DTV proof, I’d really appreciate any advice on what you submitted and what worked.

Thank you so much!