Thanks both. My route to optimise F UuA is:
AMS-LHR-SIN-BKK
BKK-KUL-LHR-AMS
I think all flights are available to book however BA.com will only offer AMS-BKK or AMS-HKG-BKK. The return BA.com does offer the flights I want through KUL - it's just the SIN outbound that I am unable to check