I’m biased but I like BKK year round. The only time I’m really not a fan is pretty much from now. Towards the end of December is the highest of seasons, and things get a little silly in terms of prices and how busy everything is. This period is technically high “season”, but the drop off after New Years is always remarkable. 
  They trickle in through Late November but they vanish like a fart in the wind the instant that Christmas-NYE party period finishes. 
  As for the rain… I like it. I got nowhere to be. I’ll sit and have a coffee or a beer, or get a foot massage, while I watch people struggle damply through the streets. (Word to the wise, buy a GOOD umbrella. Not some 7-11 jobbie. It makes a world of difference.)

Thanks for all information and advices, but I will go probably in middle june. It's rainy season but fuck it 

I'm probably going to try to make it over to LOS in the low season myself.  I don't mind rain terribly and I think that less crowds to deal with would be nice.  Just as long as the ladies aren't staying home.

The nail on the head @Unavowed. I've seen my fair share of Accor hotels (Mercure, Ibis, MGallery, Pullman, Novotel, Sofitel) and never ever had to make this amount as a deposit. I don't see ot mentioned on their website either. Anyhow, it got reduced to 5k THB (which is like 135 Euro), rather easy, so not a big issue 

Thanks for the review@Denbosch1971

Asking for a 1k deposit per day is ridiculous. You mentioned that you used loyalty points so assume you use Accor hotels regularly in which case I can only guess the deposit request is due to the location and perhaps some ‘difficult’ guests!

I’ve stayed at the Novotel in Soi 22 (or was it 24) and find this brand to be a solid choice.