Ratchada, Rama 9 and RCA: Bangkok off Sukhumvit
Most Bangkok nightlife advice keeps you on the BTS. Nana, Cowboy, Asok, Phrom Phong. A large set of soapy and massage listings never touches that line. Their addresses say Ratchadaphisek, New Phetchaburi, Rama IX, or Soi RCA, in and around Huai Khwang and Din Daeng.
That is a different evening. It is also several evenings if you treat every "Huai Khwang" pin as one walk. Din Daeng, Bang Kapi and a Rama IX soi can share a district name and still need a ride between them. Open the map before you stack three of these into one plan.
The Ratchadaphisek addresses
This is the classic soapy row people mean when they say Ratchada, and it is mostly soapy rather than go-go. Listings with Ratchadaphisek in the address include Poseidon Entertainment Complex, Emmanuelle, Alaina, Maria Massage Bangkok, Little Duck Massage and Taragon.
Dubai Luxury Club is on Ratchadaphisek 13 as well, under gentlemen's clubs. Same road, different kind of room. The category on the listing is the clue. The road name is not.
New Phetchaburi, still Huai Khwang
A second cluster uses New Phetchaburi Road and the Huai Khwang side streets, not the Ratchadaphisek frontage. La Belle, BIWA Cafe Massage, The Bank and Evita Massage sit in that band. The Bachelor (Metropole Hotel) gives a New Phetchaburi address too, as a massage listing inside a hotel name. Read that page before you assume it behaves like a street-front soapy shop.
Utopia is nearby on Watthana Tham Road. Close on a map of the district. Not automatically close to Poseidon's door.
Rama 9 and RCA
Rama IX is its own road, running toward the Rama 9 area, and RCA hangs off that side of town as a separate entertainment soi. Do not fold it into the Ratchadaphisek row.
On the Rama IX side: Colonze Massage & Entertainment, Office Massage Club, La Defense and The Great Rama 9. RamaIX Spa Club is on Rama IX Soi 43, which puts it in Suan Luang. Same road number, further out.
RCA listings are the ones that say Soi RCA: K Avenue, Kitty Spa RCA and Cbody Spa Club. If the plan is "RCA," those are the pages. If the plan is "the soapy row," go back to Ratchadaphisek.
More of both categories are on Bangkok soapy and Bangkok massage. For the Sukhumvit version of this night, use the massage sois. The rail guide for Nana and Asok will not get you here. Budget a car, or learn the MRT exits around Huai Khwang and Rama 9 from the pin you actually chose.