Sukhumvit's Massage Sois, from Asok to Phrom Phong
A massage night on Sukhumvit is not a Nana Plaza night with a different door. Nana, Soi Cowboy and Patpong are the bar streets, and they already have their own guides. The massage listings sit on the sois, and between Asok and Phrom Phong they bunch up on Soi 22, Soi 24, Soi 26 and Soi 33.
Soi numbers rise as you travel east. Asok BTS is the Soi 21 end. Phrom Phong BTS is the far end, near Soi 39. Even sois are on the south side of Sukhumvit, odd sois on the north. Soi 22 and Soi 33 are not across the road from each other. They are several sois apart, and a "Sukhumvit massage" plan that ignores that will spend the evening in a taxi between pins.

Soi 22, Soi 24 and Soi 26
Soi 22 is the Asok end of the dense stretch. Listings here include Cube Massage, Honey Bee, Maxim Massage and Kizuna Saki. The soi runs south off Sukhumvit. Once you are on it, you are no longer at the plaza.
Soi 24 continues that south-side walk. Deep Massage, Back Spa & Massage and EZ Massage all give a Soi 24 address. Soi 26 is the same idea one soi further along: Dream Heaven (Soi 26), Paradise Massage 26 and The Pixies. The names do some of the navigating. The pin does the rest.
These three sois are a plausible on-foot evening if you pick two of them. All three in one night is how people end up tired and on the wrong side of Sukhumvit at midnight.

Soi 33 is the deep one
Soi 33, on the north side nearer Phrom Phong, is where the massage list gets long. The333, G2G Massage, Casanova, Aurora 33 and Queen are on it, and so is the soapy listing AuroraMassage. Treat Soi 33 as its own stop. It is not a shortcut between Soi 24 and Thong Lo.
The full set, including sois this piece skips, is on Bangkok massage and Bangkok soapy.
West of Asok is a thinner, mixed street
Soi 18, Soi 19 and Soi 11 sit back toward Nana. They have listings. They do not have Soi 33's pile. Sukebe Nuru Massage and Lucky Cat BKK are on Soi 18. Canary Massage Bangkok is on Soi 19, which is the Asok corner. Dragon Heart is a soapy listing on Soi 11.
Soi 23 is the odd one out for a different reason. Cowboy is associated with that Asok corner, and a massage page such as Vivi Nuru can share the soi number with a bar night. Read the pin. Nana, Cowboy and Patpong is the bar decision. Which BTS stop is how you arrive. This page is for the sois those guides leave alone.
Past Phrom Phong the road changes character again. That stretch is Soi 39, Thong Lo and Ekkamai.
Open the listing before you commit to a soi. Some pages have a menu and hours, some have an address and a pin and nothing else. The map is how you check two "Sukhumvit" pins are actually on the same soi.