How suitable is a Dahon folding bike for Indian road conditions?
Unfortunately, I think this bike would be a poor choice for a number of reasons.


First, the small wheel size will accentuate the bad road
conditions. Larger wheels will seem to smooth out the bumps a bit
better.
As has already been commented, folding bikes in general do not handle particularly well, which is not what you want on bumpy streets.
Although this bike folds, that is the extent of its portability.
The Dahon website says it weighs 31.7 pounds, so it's going to be
difficult to heft even though it may fit a bit better on a train
than a non-folding bike.
My experience with Dahon is that you pay quite a bit for the
foldability. It looks like this bike costs $300. When you consider that $300 is the starting point for "bike-shop brand" bicycles, a $300 folding bike is, frankly, using probably the lowest quality components possible. Not ideal for any riding environment and made even worse by rough roadways. I suspect this bike will cause you quite a few maintenance headaches.


I don't know anything about trains in India, but if it is possible to bring a non-folding bike onto a train there, I think you will be much better off overall. You will get more bike for the money, probably a lighter bike, and definitely larger wheels. My advice would be to shop around for something of the non-folding variety if your budget is $300. I would look at a mountain bike if the roads are extremely bad, but for more weight savings a hybrid would be an option.

I don't know the bike shop situation in India, but the folks at a bike shop will probably be able to guide you to something that is appropriate for your local riding conditions.