My last visit was half year ago, hope the info is still up to date.
As i remember they used to have only two price for girls in fish bowl and a few sideline sitting on the sofa outside, however, they moved those sidelined inside the fish bowl later on (probably because of regulation). So that make it possible for 3 price group but anyway, you can ask those Papa san, they will explain to you (some of them can speak chinese). In general, girls in uniform are those normal BG (THB2000-2500), girls in their own outfit are sidelined (THB2600-2800, or maybe up to 3000). These price are supposed are the only charges you have to pay, i.e. including girl and room for 90mins to 120mins. However, they will ask you in the room if you want drinks (ice tea, coffer, coke etc, one for you and one for the BG). To be polite, normally you are recommended to order these drinks, it will cost you app. 100-150 THB for 2 drinks depending on different Massage Parlor.
All models are on 3rd floor price range fm THB 3000 to 5500 (90 mins). Mama san can show you photo for those took photos for Magazine like: Penthouse, Cute etc.
Regarding all those rooms, normally you don't get to choose those rooms, after picking the BG, they will asign you a room (no matter is BG, sideline or models), you got similar room. Except you are willing to pay extra, then you get the party room which is much bigger with Karaoke. Actually, only local big spender will pick these rooms. Poseidon also has one room on the top floor with big Jacuzzi.
About your question on Body Massage, if you are referring to those services on a mattress (Water Bed), then you may not find it in Poseidon. As i remember, you may find 1-2 girls in Nataree and 8-10 in Emmanuelle providing this services at around 2500 for 2-hr (but they are not young).
Hope these info help and have fun in the LOS
