The Atlanta Hotel has a rich history, built in 1952, it has the first swimming pools in Thailand. i had never heard the anti venom story in the wikki. They even had a yacht on the Chaopraya. The original Art Deco lobby remains unchanged.
https://en.wikipedia.org/wiki/The_Atlanta_Hotel_(Bangkok)#:~:text=History&text=The first owner of The,Company to manufacture snakebite antivenom.
The family is an odd one, after being something of a haven for drug smugglers in the 70s, things took a very moralistic turn. Even today, while they have lightened up they is still a chance you will be turned away or asked to leave the premises, if they don't like the way you look.
I haven't eaten in the restraunt since before COVID but one page of the meu used to (and still may) says this:
The clientele is very specific, return visitors, NGO's anyone seeking oasis in the area. The rooms are plain and the pool has seen better days but it is still remarkable.
Sadly the woman who ran the coffee shop passed last year and with her went some of the most wonderful inexpensive Thai food in the area. I used to eat there often, others tried but were unsuccessful.
I have several friends who begin and end their stay in Bangkok at the Atlanta and have been doing so for years. i always take time to spend a day by the pool when they do.