The Singapore National Registration Identity Card (NRIC) is issued to Singapore citizens and permanent residents. 

Citizens and permanent residents are issued with identity number starts with prefix S (born before 2000) and T (born in or after year 2000), followed with a 7-digit number and a checksum alphabet.   For citizens and permanent residents born after 1968, the first two digits of the 7-digit number indicate their birth year.

You can visit the government page for more info: