I've not done a single speed conversion myself but it doesn't look much different from some SS cross bikes I've seen, which uses a band-on chain tensioner instead of moving the wheel around in the dropout to stop the chain being dropped.
This is one that has been on my local circuit this year. It now has a chain tensioner after the chain got dropped in round 2... And hydraulics. I think this photo's a bit old tbh.
I'm afraid it's a handmade frame!