Hope it goes well for you this time. Let us know. One of my very good friends who I used to work with had a "Difficult" passport. Needed visas for everywhere including Thailand. He spoke at many medical conferences globally as he was senior in his field. Now he took Singapore Citizenship. Can travel almost anywhere visa free.
As for DVT and nationality it is 100% true certain nationalities and locations are scrutinised more than others. Officials have pretty much said it without saying it directly. Same as in other countries like Vietnam. Certain passport holders very much restricted without being a published list.
It is nuts and some places more nuts than others lol. Each locale seems to have it peculiarities and specialisations. That is about as much as I am posting in public lol Prices for certain visas have exploded recently too.
This is Ed visas being monitored. DTVs are not right now. Someone running a bar on a DTV though is open to being taken advantage of. Could be dobbed in or made to pay up. There are people on DTV openly flexing on TikTok about running a business in Thailand on it and touting for customers too.