google

Agoda do have good price , but I find once you find the hotel you like do a google search on it and google will show you a list of price and often the price listing on google is cheaper then search under Agoda for the same hotel Example: GOOGLE - AGODA - $100 Search inside AGODA - $110  

I'm a nightmare for checking for a bargain, I'll have Agoda, Booking et al, all open on different tabs, including the hotel direct, plus Topcashback too, to see if any of the sites have any cashback offers. For my upcoming trip, I have a saved enough for a few ST, even if the cashback will take forever to come through 

Use Trivago: https://www.trivago.com/  It will give you a view of the prices. Usually Agoda, Trip.com, and booking.com give you the lowest prices. If you definitely want to stay on Soi 11, try NISA hotel: https://www.nysahotelbangkok.com/  If you do not mind to walk a little bit, opposite Soi 11 is Soi 8 with several hotels. I like Adelphi Suites there: https://www.adelphihospitality.com/destinations/adelphi-suites  

Keep an eye on prices. They often drop if vacancies remain high. Sometimes I find booking direct is actually cheaper than going through one of the consolidators like Hotel.com or Agoda. It's always worth checking them all.