There are 12 direct and indirect flights connecting Istanbul and Singapore every week, with the journey taking 23 hrs on average.
Or, if you're fairly flexible on dates, try to get a last minute-deal by regularly checking the Netflights website.
In Singapore, Singapore Changi International Airport (SIN) is usually the cheapest airport to fly to, but there are one airports to choose from. Not sure who to fly with? British Airways, Lufthansa & Turkish Airlines are the most popular airlines available from Istanbul.
If you can’t find flights that suit you, consider flying to a another part of Singapore.