Hi!
Let me give you some advice.
I recommand flying at 6:50pm about NRT-BKK.
I'm affraid you can get on the flying at 4:15pm.
Your immigration is maybe no ploblem.
But if DFW-NRT flight will be delayed over 1 hour,you cannot get on the JAL 703 NRT-BKK flight.
Naturaly,JAL has good grand staff who will give you best effort...
I thing It is no good way.