So far I only knew about two cities which have an additional subdivision into subdistricts (Khwaeng, แขวง) additional to the boroughs (chumchon, ชุมชน) - Chiang Mai and Nonthaburi, though only for Chiang Mai I have found a list of all the municipal subdivisions on their website.
As I monitor changes to the Wikipedia page "Administrative divisions of Thailand" making sure nobody removes the link to this blog (just kidding), I noticed a change last week suggesting that Pattaya and Hat Yai also have this additional subdivision. The user Marut28 who did this change in past had done several good edits, especially related to Surat Thani Province and Chaiya, thus I trust his edit to be correct. The bad thing - this user never ever replied to any questions posted on his talk page, so trying to ask him for a reference probably won't give me any answer this time either. I tried to look at the websites of both Pattaya and Hat Yai, but failed to find any page listing their subdivisions.