It also strangely helps that Singapore has almost no natural resources to exploit. So, their only resource is what the humans provide. That lead them to invest heavily in professional training instead of using their humans to pull metal out of the ground and ship it off somewhere else.

Not a natural resource per-se, but Singapore's geographic location is very special wrt global trade and strategy, being at the tip of the Malaysian peninsula and in the Straight of Malacca. It's been a port and a nexus as a result for hundreds of years, a huge part of the equation of Singapore's success story.

edit: wikipedia says 25% of the world's trade flows through the Straight of Malacca - it's a big deal!

I strongly second this -- this was also one of my main takeaways from my research on how Estonia modernized and became quite prosperous (especially relative to where it started post re-independence from the Soviet Union).