Hi, it's good to know that there are still somebody interested in architecture. Haha.
I am currently a year two architecture student in NUS, i got in with my STPM result two years ago, and i did not have straight As.

I am not that sure about industrial design, but usually architecture will require you to come for an interview and aptitude test, same as any other architecture school. For NUS, almost every year it's about making a 3D model with some cardboard paper on a given topic, and you would have to explain your intention behind the design. Do come prepared, read up on some famous architects and stuff. I am sure you will be able to find more discussion about this online.

As far as competition, I think it's the same as every other course in Singapore. The competition is tough, and the course itself is not easy. "Are you staying over in studio tonight?" is one of the sentence i heard the most while i was in year one. But it is definitely a fun course, I get to do all kinds of interesting stuff like building timber structure and casting concrete, and there are less textbook to memorise and tests to prepare for.

Do read more and prepare for the interview. Show your passion in the field, architecture is not about drawing nice buildings.

It's a little long, but hope it helps!