I tried a BKK-SIN-HAN-SIN-BKK and was quoted THB 47,000 for flexi-saver fare.

Booked it as two sectors, and paid THB 9,200 BKK-SIN-BKK, and SGD 535 (THB 12,700) SIN-HAN-SIN for a total of THB 19,900.....period of time in SIN is less than 24hrs both ways. Same flexi-saver fare class

Quite a few message 'server experiencing extreme demands at the moment, try again later'. I preferred the 'old' website...