I believe this image pre-dates 1900.....[mid/late 1890s??] when the no. 3 line routed itself extensively from The Grand Palace to Klong Toei - before modifying to the Dusit Line, which principally served the immediate Rattanakosin area. That area was still quite wooded well into the turn of last century. I'm guessing the road aside the tracks is a more southerly section of Maha Rat Rd or Sanam Chai Rd.