I mentioned the low number of visitors to the district museums earlier, but now I have found actual numbers to illustrate it.
As the second endnote "ข้อมูล ณ เดือนตุลาคม 2548" says the visitor data is from the October 2005. The number differ quite strikingly - while Thawi Watthana and Bang Khun Thian both have about 1000 visitors, the one of Nong Chok only got 10. This is even more surprising as all three mentioned are in the extreme outskirts of the city, Thwai Watthana and Bang Khun Thian to the west and Nong Chok to the east. The one of Phra Nakhon close to the touristic centers got just 312 which still made it number 5, or Samphanthawong then still in Wat Traimit at number 8 with 260. In total the 27 museums received 6622 visitors, which means about 250 per museum, around 10 each day.
However I guess these numbers are not really usable for anything more than a rough overview. The fact that the two westernmost and remote museums received most visitors can only come from some busloads of students carried their from their schools, so the activity of the school in the district distorts the numbers for the corresponding museum. For a more meaningful statistics these visitors should be listed separately from those visitors coming out of their own initiative.
Taking into account a comment of the guide in Bangkok Yai museum that the visitor numbers went down a lot since the end of the Thaksin administration, any more recent such statistics would probably be devastating. Which is really not a fate deserved by these museums, and I really pity the guides who spend most of their time just waiting for a visitor. The only way out would be better promotion, but with the museum website http://www.bmalocalmuseum.com offline for more than a year, and even more an email regarding these museums sent to the Bangkok tourist office getting no answer I have not much hope for any improvement.