Fellow neurotic light sleepers, what hotels do you recommend that are off of the Sukhumvit BTS line?  

The search here is actually really good for finding things like this.  For example, searching (everywhere) for hotel quiet sukhumvit, then clicking on the highlighted part below to AND the three keywords together will cut the 136k results down to 184 total (showing only threads which contain all three of those words).  You can then sort by date and focus on the more recent threads.  

 

I'm also a quiet freak and remember reading and taking notes on the thread below which was created last month.  Key Premier and Dynasty Inn (specifically the new Standard rooms in back of building) are mentioned within it as being quiet, but you'll probably find lots of additional options using the search.  Feel free to update your thread with any notes you make, it will help others who search in the future.  There is also the sister site (https://bangkok-addicts.com) which may contain additional info.