We've scanned every flight from Johannesburg to Singapore to find the best deals. If you want a cheap flight, it's best to be as flexible as you can on dates. If that day's no good for you, try searching by month to see some alternative dates.
Singapore Changi International Airport is just one of the airports in Singapore. If you're not set on a specific airport, try changing your search from Singapore Changi International Airport to Singapore to see a broader range of flights – they might be cheaper.
If you're planning on going to Singapore during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.