The Pattaya soi (Thai for "small street") most densely populated with short time bars is Soi Six which is also named Soi Yodsak. It runs from Beach Road 1 to Beach Road 2 and is located between Middle Road and North Pattaya Road not far from Big C shopping center.
Soi Six also has some good western cuisine restaurants. Here is a great hotel to stay at in this area. It is 3 minutes walk to Soi 6. Book on line to save 20%.
The most popular short time bars seem to be located in Soi 6 Pattaya.
More about Soi 6