Observe the reason Japan invade Manchuria, we can find the reason. Manchuria has very rich natural resource, good agricultural productivity, abundant mineral storage of iron and steel, copper, gold, silver and coal. Japan needs these resources to support their industrial development and solve their financial crisis after 1929. So I believe if they will attack south East Asian, the only country they will attack is Indonesia. Because these is very abundant Oil storage in Indonesia .
Oil is very critical for their industry development.
So even if they invade south East Asia we are not their target country to attack. I agree with FM s conclusion. Look at Japanese institutional structure and interest group, we can find who is on power, who is decision maker. In Japan, Military politics play a key role in today s Japanese Policy making procedure. Military interest representative already occupied important position in their government, organized a militaristic government.