The district offices in Bangkok are normal office buildings, and don't look like the district offices of the other provinces, quite clear because the land prices in Bangkok are much higher and thus the building style has to be more space-saving. Also, as the districts of Bangkok are a different administrative entity, the offices also have a different name, สำนักงานเขต, Samnak Ngan Khet.
The district office of Bangkok Noi is the closest one to the place we usually stay when we are in Bangkok, at least for a farang still in walking distance. It is located directly next to the Khlong Bangkok Noi, once a meander of the Chao Phraya river reduced to a canal when the main course of the river was changed by digging shortcuts. Nearby the district office is Wat Suwannaram Ratchaworawihan, once an important temple. It was used as the royal cremation site in the beginning times of the Rattanakosin era, and the actual location of the crematorium is now the location of the district office. The temple is famous for its murals, however the two bot/viharn were both closed, so I could not take a look. At least from the outside they also look like in need of a renovation.
Adjoing the temple is the Suwannaram Witthayakhom school, where one room was converted into a museum of the district, part of a program by the Bangkok Metropolitan Administration to have a local museum for every district. The signs within the museum are bilingual, but sadly none of the guides could speak English at the time I visited, so I could only get the written information. I have to revisit it, last time I did not take photos of it. Tour-bangkok-Legacies has a review on this museum, together with a map how to find it.