The rainy season is actually a good time to visit Pattaya. The storms also bring cool breezes which is a relief from the hot temperatures. Rain rarely lasts for more than a few hours. And if you need to go somewhere, you can buy a plastic poncho from 7.11 for a cheap price of 20-30 baht. This will protect your clothes from getting wet but you may want to wear waterproof shoes.
Of course the girls of soi6 don’t stand in the rain but because there are less customers browsing you will get more attention and can usually take your pick.
Hotel prices in the low season are also cheaper compared to high season. This means you may be able to negotiate a discount if you simply walk in to a girl that you like rather than pre booking.
Storms can sometimes cause flooding which disrupts traffic on the highway but once you are already within Pattaya, it will not be a problem if you have chosen a hotel with a good location.