I’ve been to Bangkok. Open sewers; too.
But that was 50 some years ago...
I just spent several days in Seoul...a bustling city of 26 million. To give you an example of how advanced it is...there 291 subway stops and 32 river bridges. It is incredibly clean...cleaner than any US city we’re seen. Everyone was nice and helpful. We never felt threatened or uncomfortable. They have great WiFi connectivity. As long as the mentally ill north Koreans don’t mass murder them, they’ll do fine.