The Avarin shop that is not next to Tarntawan Hotel has massage rooms on the ground floor just behind the foot massage lounge.
Chaichana on Patpong Soi 1 has massage rooms in the basement, just one floor below its foyer. The stairs down aren't difficult.
Prime has ground floor rooms in its third building, though Prime is not known for offering a milking service to conclude a massage.
There is also one shop on Silom Road under Saladaeng station that has ground floor rooms but unfortunately I can't remember which one it is. But you could easily walk that 100-metre stretch and ask the boys out front of each shop if their rooms are on the lower floor.
Further afield from Silom, Prince has ground floor rooms as does Jey Spa.
The above is based on memory which may be a little faulty, so please double check my information with the shops themselves.