Much like "happiness", the concept of "national peace" is difficult to measure. The Institute for Economics and Peace created an index for measuring just that: The Global Peace Index (GPI) uses a weighted average of 23 quantitative and qualitative indicators, measuring both "Internal peace" (for example, the level of violent crime) and "External Peace" (for example, relations with neighbouring countries).
According to the recently published survey of 2011, the three island countries of Iceland, New Zealand and Japan top the list of the most peaceful countries in the world. The survey places Bhutan at the respectable 34th place, advancing 2 places compared to 2010. Bhutan's rank is way above that of other South Asian countries (see table). Note that the Maldives are not surveyed. The full report can be downloaded here.