Recently went May period. Leaving the below here in case it might help;
Day 1 - Singapore - Istanbul
Day 2 - Istanbul (Topkapi palace, Blue mosque, Hagia sophia, Basilica Cistern)
Day 3 - Istanbul (Chora museum, Suleymaniye mosque) - Cappadocia
Day 4 - Cappadocia (Hot air balloon, Goreme open air museum)
Day 5 - Cappadocia (Sunset point, Green tour)
Day 6 - Pamukkale
Day 7 - Selcuk/Ephesus
Day 8 - Selcuk - Istanbul (Bosphorus cruise)
Day 9 - Istanbul (Dolmabache Palace) - Singapore
My personal preference would be:
Cappadocia>Pamukkale>Ephesus>Istanbul
Make sure to leave 2 mornings for Cappadocia in case the weather does not allow flying. Out of my 2 mornings, only one morning was suitable for flying, and we got lucky while listening to other tourists who missed their bucket list item.