I don't think the second one would work since you already turned around at HKT, BKK-HKG would be considered backtracking if you plan to fly HKG-IST. Remember after your destination, you can either continue going east, or turn your heading towards west.

I have a question for the experts though, I planned to arrive at ZRH and open-jaw to CDG. Would this be allowed? Also, my trip includes a leg of KUL-SIN. If I remembered right, one cannot travel a greater distance in an open-jaw than the shortest leg on the itinerary.(ZRH-CDG 297mi, KUL-BKK 185mi) Is it likely that the booking agent would give a bit of leeway or not even knowing ZRH-CDG is farther apart than KUL-BKK?

Thanks