There are 2 types of public companies in Singapore.
The first type is one which desires to raise capital from the public. It includes all those companies whose shares are listed on the Singapore Exchange Limited (SGX), either on the mainboard or the secondary board known as Catalist. A company with more than 50 shareholders is a public company even if its shares are not listed.
The other type of public company is a company limited by guarantee. These are commonly used for charities or to serve other national or public interests.