Thanks for all the infos and advices 

One good thing about going in the low season is that the bars will be relatively empty, compared to the high season and you can have a larger selection of girls. Though when I went to CIB11, it was always full the last few times I went!! So yes, anytime of the season is great. I myself prefer the low season as relatively less crowds!!  

Any recommendations on where to buy Prep and Doxy PEP in Sukhumvit (lower or upper)? thx

Provide us the details, I need to get my ears lasered lol

I totally agree with the above. I've visited many times in both, low and high season. Specifically July, not since 2017, but more recent in June and August. Just got home from 2,5 week trip Aug/Sept. And to answer your question: Yes, it does rain most days. But did it obstruct any of my plans: no!  Just bring a good umbrella, or buy one on the ground (bought mine at Robinsons, corner of Soi 15), and you're good to go! Prices for hotels are definitely more appealing in the low season!