I was doing a little OSINT hacking on a number of Singapore addresses and came across a very cool little tool that allows you to easily work out which districts in Singapore post-codes are located.
Singapore is divided into 28 seperate districts as outlined below

Singapore postcodes are administered by Singapore Post (Singapore's designated Public Postal Licensee which provides domestic and international postal services). The postcodes are all six digit consisting of the sector code and the postal delivery point. The sector is represented by the first two numbers of the postal code. The remaining four numbers define the delivery point within the sector. However, they are not easily correlated just by looking at the 6 digit code for instance postal code: 208642 is located in sector 8.
District Code Finder
The following link provides a nifty little district code finder, that can help plot out different addresses in different districts.
List of Singapore District Codes
Below is a table referencing all the districts, postal sector and general location.