Yes it’s fine it’s equivalent to your local currency. You could if you wanted to be extra, supply a page showing the conversion from your currency to THB. Try to keep it at around 550, because currency rates can fluctuate daily.
The first thing I’d suggest you do, is contact somebody in Thailand (an agent or similar) who can verify whether you are actually Infact on a blacklist in Thailand. Please try to use a reputable one.
As far as im aware, It’s uncommon to be blacklisted for this reason, but there may well be a note on the system to indicate that you were refused entry & subsequently returned to your port of origin.
I’m sure you’ll know this, but don’t try to reenter again, unless you have a relevant visa, be it DTV or tourist.
After that contact with the embassy in London, if you do apply for the DTV in the future, I’d recommend doing so from another country. ✌️