take a look at the missionzones-4 areas
iirc the alienbases are located in these areas and southeast asia has 4 (in indonesia, philipines, china, japan) with 3 of the 4 areas very small
getting 4 alienbases in the same region instead of a more equal distributution in the 4 regions could be bad luck or sign for a buggy selection code?
who want to test/read code?