NUS no longer offers accounting. You need to go to NTU or SMU
for that.
I'm not sure about environmental engineering. But while chemical
engineering has good prospects, it is arguably the heaviest and
most difficult engineering field.
In the end, just choose whatever interests you the most. If FASS is
your main interest, there go forth and be an Arts major. Listen to
your own personal interests, and not the flow and ebb of the
economy.
After all, in the late 90s, the 'in' thing was IT. Then in the
early 2000s, it was the life sciences. Now, it's the integrated
resort. And at the same time there have been complaints that we
don't have enough civil engineers: http://www.todayonline.com/articles/171459.asp
Get the drift? So just do whatever you enjoy the most.