Comparative advantage is an economic theory which claims that all countries will be better off if each of them concentrate on doing the things it does best. For example, a country that produce cotton and cotton textiles efficiently and cheaply should concentrate on this.
Some countries have one thing they do better than anyone else. They may have a natural resource like coal or rubber, or a climate which is perfect for growing, say, bananas. By concentrating on one activity they can import the things they produce less well.
Singapore has not any advantages, but the government turned its people into its advantage. They developed a highly-educated workforce and know-how in manufacturing high-tech goods.