http://www.straitstimes.com/politics/singapore-and-myanmar-announce-visa-exemption-for-30-day-trips
It's rare that the developed country admits visa exemption for citizens in developing nations. I'm sure that promoting reciprocal economy or interaction is one of the reasons for visa exemptions. But, it won't be the essential background. Another reason will be Singapore's hope to take part in Myammar's market, which is being liberalized.
