You are leaving at 10 pm arriving at 2 pm+ .
After sunrise (which is when everybody is sound asleep ) it is cloudy anyway and your fellow pax can become pretty nasty if you open your shade and disturb their sleep. F and C on this route is mostly used by business people who connect in BKK or continue to SIN.

Why do you want to stare at the dark night for most of the flight? Eco on the other hand is full of touris happy with the free booze who do not want to sleep and keep their shades up for the whole flight.