There are a few bars in Bangkok that sort of defy description and get lumped into the category of 'specialty bars'.

The first one I want to mention really isn't a bar at all in the general sense of the word because they don't encourage people to sit around and drink. I'm talking about The Eden Club on Sukhumvit Soi 7/1. At The Eden Club you're greeted by a line up of ladies and you're expected to choose two ladies. If you don't see anyone you like you'll be politely asked to move on, because Eden is not a place to hang out and drink. Most guests choose a lady and then let her choose the second. This ensures good chemistry between the ladies as they like each other, but you can choose both ladies if you want.
The cost is 3600 baht for 90 minutes with 2 ladies.
Takeaway service is also available.

Another bar that fits in the category of specialty is Lolita's located on Sukhumvit Soi 8. At Lolita's there are usually a few ladies hanging around outside the entrance, you can choose one or just go in the bar and one will follow you in.
Once inside you can order something from the bar and maybe a drink for your new companion who will be asking if you want to go upstairs. The cost to go upstairs is 700 baht for a bj in a curtain stall with a couch, I usually tip 200 baht on top of that if the service was good.

Go-go bars aren't for everyone. A lot of people don't like the loud music, high drink prices, and crowds associated with Bangkok A-Go-Go's. Some guys just don't want to pay a barfine of 500-1000 baht that most go-go bars charge.

While I think go-go's are a good place to find beautiful women in Bangkok, I'm going to list some alternative places. While some of these places are bars, none of them will charge you a barfine because the girls there don't work for the bar.

Daytime.

Biergarten- Sukhumvit Soi 7.
The Biergarten is a popular freelance hangout. Located almost directly across the street from an outdoor food court (which is one of my favorite places to eat).
The Biergarten can get quite crowded, especially on weekends when it can be hard to find a seat. But there are usually plenty of available women at the Biergarten so it's worth a look.

Gulliver's- Sukhumvit Soi 5.

Gulliver's is more of a regular restaurant and bar with a lot of pool tables and a few working girls. You can't assume that every girl here is a p4p girl so you need to be a little discreet.

Golden Beer Bar- Sukhumvit Soi 4.

Golden Beer Bar is on Soi 4 almost directly across the street from NEP and next to the Nana Hotel. Usually a freelancer or two will hang out here during the day but some may be just leaving a customer at the Nana Hotel and looking for a new customer.

Night time.

Thermae Coffee House- Sukhumvit Road, below the Ruamchit Hotel.

The Thermae is still a freelancer hangout and you can still find some gems here.
On my first trip to Bangkok, Thermae used to stay open until 6-7am. But now closing times are being strictly enforced and most bars follow the 1am closing time with some hotel bars being allowed to operate until 2am.
Really a must see for any new visitor.


Angels Disco- Nana Hotel.

Angels Disco is packed with freelancers every night and is a great pick up spot. Of course the disco is as loud or louder than most go-go bars so that might turn some off.
After closing time a lot of the girls will congregate outside in the Nana Hotel carpark or along the sidewalk, until the police or hotel management chases them off. Be careful here as a lot of ladyboys will gather here at night.

CM2- Novotel Hotel, Siam Square.

This is a more upmarket venue and is not for everyone but at CM2 you will need to dress a little better than if you were just planning to go to the go-go's.
The ladies asking prices will be higher at a venue like this so be prepared to be quoted prices in the line of 4000B short time and higher.
There are usually some Eastern European hookers hanging out at CM2 and similar venues.

There is a lot to do in Bangkok, but for the purpose of foreign tourists, there are 3 main "entertainment areas" I want to focus on first. Not to say this is the only nightlife available to tourists, but for the first-timer, these 3 are almost a must see.

First on the list is the famous (or infamous) Patpong.
Patpong is actually 2 streets running parallel between Silom Road and Surawong Road. Some would argue that Silom Soi 4 and Soi Taniya are part of Patpong, but for the sake of this article I'm only including Patpong 1 and Patpong 2.

Both Patpong Streets are lined with vendor stalls at night and the streets are closed to traffic. It's very crowded and difficult to make your way down the street most times. Add into the mix the touts that line the street trying to convince to enter the various bars that line both streets.
Patpong has over 100 bars lining the streets including an array of sleazy upstairs bars most of which you'd be better off avoiding.
The ground floor bars are mostly a-go-go's with bikini clad women dancing on stage, the most popular are the King's Group bars such as King's Castle I, II, and III, Queen's Castle, etc. Goldfingers is an American owned bar on Patpong that is very popular.

Patpong Menu

Most of the upstairs bars offer some kind of show where the dancers open bottles, shoot darts, shoot ping-pong balls, etc. using their vaginal muscles. Some offer a live sex show.
There are always reports of rip-offs at the upstairs bars, the bar will add an 'entertainment' charge to your bill or pad your bill with drinks you never ordered. The best thing to do is pay the bill and get a receipt and take it to the tourist police at the Silom Road end of Patpong. They will go to the bar with you and can usually get your money back.
But the best thing is to avoid the problem altogether and only visit reputable bars such as Queen's Castle, Pussy Galore, or Firecat.

Another thing most of us want to avoid are the katoeys (ladyboys) at Patpong. King's Castle III has mostly katoeys dancing there, King's Corner is also mostly katoeys.

Located on Sukhumvit Soi 4, almost directly across the street from the Nana Hotel, Nana Entertainment Plaza used to be in my opinion the best nightlife area in Bangkok.
Nana is still worth a visit, and you can still find some gems here, but the place just seems to be regressing year by year.
NEP is a three story plaza with an open courtyard. Open-air bars are placed in the courtyard and the surround plaza is filled with bars. There are 4 'Rainbow' bars: Rainbow 1, Rainbow 2, Rainbow 3, and Rainbow 4. These are some of the most popular bars at Nana, especially among the Japanese patrons. Angelwitch is also a popular go-go, as is Voodoo. Some of the other bars at NEP are: Mandarin, Carousel, Lollipop, Fantasia, and G-Spot. The Katoey bars are Obsession and Casanova.
NEP also has a 'short-time hotel on premises for those times when you don't want to take the girl back to your hotel room.
Bar fines are usually 600 baht, other fees need to be negotiated with the lady.

One thing to remember is to make sure that lady you're picking up is really a lady!
Ladyboys are everywhere in Thailand where there are tourists. It might take some practice to be able to differentiate the katoeys from the actual ladies but here are a couple of tips to prevent you from getting a nasty surprise back at your hotel:

1) Be cautious of very tall girls or girls with large breasts.
Thai girls are usually small and petite, so if the creature you are talking to is 6' tall with a 38DD bust there's a good chance it's not a she.

2) Look for large hands and feet. Again most Thai girls will have small hands and feet, the males can put on a dress and makeup but they can't change the size of their hands and feet.

3) Aggressive behavior. Katoeys are usually aggressive in their approach groping you, or inviting you to grope them (watch out for pickpockets in this instance), while the ladies are usually more subdued.

If you want to avoid katoeys (or if you want to find them) here's some places where they are known to frequent:

Katoey Bars

-Casanova in Nana Entertainment Plaza.

-Obsessions in NEP

-King's Corner in Patpong

-King's Castle 3 in Patpong