Ultimate MRT bike?

I have been using a folding bike to commute with MRT since 2004. I bring it along everywhere I go, because  I am worry that it can be stolen easily. The advantage of this approach is that I get to use my bike everywhere I go, from home to MRT, from MRT to office, or between shops when running my errant. Over these years, there is constantly a question in my mind:

"What is the ultimate bicycle to be used for commuting with MRT?"