You need stop turnaround stop. So you could do SIN (stop) - BKK (turnaround) - HKT (stop), if there is any other route on *A from HKT. Otherwise, you could do SIN (stop) -BKK-HKT (turnaround) - BKK (stop).
Also, if you give me your depart city, I'll give you MPM for all these cities.