You've got two stopovers, which is not allowed. You need to depart ICN by 1724 on 29 November (or arrive after 1920 on 28 November), as otherwise the layover exceeds 24 hours and becomes a stopover. You've already got a stopover at LAX. The system is pricing it correctly as a BKK-GRU-ICN open-jaw with a stopover at LAX plus a one-way ICN-BKK. Since DL doesn't do one-way awards at half of RT pricing, you pay 45K for that.