Simplest is to drop SYD. Note that CCU is near the upper limit of a PPS earning band, DEL would be better purely from PPS earning viewpoint.

BKK-SIN-DEL-SIN-FRA-JFK-YYC-YVR-ICN-SIN-BKK has about 1360 miles to play with and earns in C the following number of PPS sectors (assuming on SQ)

BKK-SIN 1.25
SIN-DEL 2.5
DEL-SIN 2.5
SIN-FRA 5
FRA-JFK 2.5 (must be separate flight number or stopover at FRA)
YVR-ICN 3.75
ICN-SIN 2.5 (must be separate flight number or stopover at ICN)
SIN-BKK 1.25

total 21.25