Singapore is advanced and rich, but it is small compared to Indonesia. Singapore has larger GDP and military per capita, but in absolute terms, Indonesia is much larger. Its army has four times as many men as Singapore (300,000 vs. 75,000), and Indonesian GDP is 2840 billion USD while Singapore is 453 billion.
Not agreeing with the previous statement regarding Singapore's military supremacy, but measuring military effectiveness by number of troops is a hopelessly outdated method.
Powerful armies are nothing more than logistics organizations, with 80-90% of members operating supply chains and maintenance to enable the 21st century weapons systems and their elite operators to destroy things.
300,000 guys with assault rifles and crappy Air Force are no match against 75,000 with modern technology and precision munitions.
It also depends very much on the rules of engagement. 300,000 guys with modern technology, precision munitions and a government with strong human rights legislation have a hard time against 75,000 men with assault rifles, improvised munitions and no limits on what they can do to their enemies.
(edit:typos)