All--

I've done NRSA to/from BKK many times and never been left behind.. that being said, it can be very hot or cold within the same week.. If I suspect that I'm going to have trouble getting out in the morning (I travel from BKK back to west coast USA, so all my departures are early AM from BKK) I look at these options (in order of my personal preference):
1) Get a SIN-BKK late evening flt the day before and get out of asia via SIN.. lots of discount carriers ply that route so it may be cheaper than an ID and you're a rev. pax., or 2) Explore alternate departure points for my return USA bound trip such as TPE/HKG/ICN/KIX/NGO/PVG/PEK.. All these points have non-stop AM flights out of BKK and can connect with a USA bound departure.