Since you mention practical application of learning a foreign
language, I will assume that your preference in terms of the 3 are
equal.
Malay: A good regional language as our closest neighbors are
Malaysia and Indonesia. Given the water-treaty agreement between
Singapore and Malaysia, perhaps a good grasp of the language would
put you on par with the Malaysian-born Chinese that are in the
fields of Water Technology?
Japanese: A somewhat less useful language as the Japanese language
is predominantly used in Japan only and rarely conversed outside
its borders.
French: A secondary linguistic option to be considered besides
English, in terms of the European context. Do bear in mind that
even though English IS the most widely used language for
instruction, major European powers like the French and Germans
still prefer to use their own language for conversing. Learning
French would definitely be a useful tool and advantage should you
consider getting hired by a European-based firm that has its
operations in Singapore/Asia.
