1. Wait and hope you can find low mileage award tickets on DL (or partner).
2. Book a cheap economy ticket on UA or TG and then try to buy a cash upgrade at the airport. If they are selling UGs you can do it for about $2400 in total, but you may end up stuck in coach.
From BKK to CNX, it's either TG or AirAsia. You can buy the ticket at BKK if you need to.