Korea and Japan rose from the ashes (Japan having lost WWII after their imperialist ambitions failed) in the same amount of time. Korea had a dictatorship or sorts but Japan didn't, but unless I'm mistaken, neither government was as autocratic (and still is) like the PAP is today.
The first Korean Republic (1948-1960) was vastly more repressive than the PAP at its worst, let alone today. Mass arrests of political opponents, reeducation camps, massacres: you name it, Rhee did it. The second republic (1960 to 1961) was theoretically a liberal democracy, but got couped almost immediately. After that, South Korea remained a somewhat milder developmental dictatorship, ala Singapore, until 1987.
good question, maybe because their neighbouring countries have a strong relationship to a certain religion (1) and (2) SG used to be a GB colony like HK which is doing great as well.