It’s not an error – just a crappy routing.

24-hours or less is considered a valid connection on an international itinerary… the routing displayed to you is one way to get to BKK departing on the 20th. Of course, you could also depart the next day and connect via DTW/MSP and simply your journey.

I've gotten routings like CUN-MEM, MEM-DTW (next day) many times...