Singapore, as a city, was a creation of the British. In 1819, Sir Stamford Raffles founded Singapore as a trading post of the East India Company (with permission from the Sultanate of Jahore).

There were settlements there previously, (though not very substantial). In 1613, Portuguese raiders burned down the settlement there, and there was not much established until Raffles came along 200 years later.

In 1824, by treaty with the Sultan of Jahore, Singapore became British.

Although Singapore was ruled at times by the Chola Empire (before 1613) by the Sultan of Jahore (from 1613 to 1824), by the British Empire (fr0m 1824-1942 and 1945-1962), by the Japanese Empire (from 1942-1945), by Malaysia (from 1962-1965) and since 1965 as an independent country, and so, was part of bigger countries or Empires, Singapore itself was never a bigger country or civilization than it is today.

Singapore as an independent entity is relatively new. It declared independence from the United Kingdom and joined the Malaysian Federation. For a number of reasons there was quite a lot of tension between Singapore and Malaysia. This eventually led to Singapore being expelled from the country. As far as I as know, this is the only instance of a country gaining independence against its will.

Bonus factoid: according to the Malay Chronicles (Hikayat Merong Mahawangsa), Singapore was founded by a descendent of Alexander the Great. Yes, that Alexander the Great. He was said to have married an Indian princess and a remote Hindu descendent founded the state that would become Singapore, before moving to Rome (!).