How does Boeing Deliver single aisle jets to South east Asia?
Magic. More specifically, science.

Even regional aircraft are generally designed with 3,500+ nmi range with some load, and more without. It's more than enough to travel to anywhere in the world, given some refueling stops.

In fact, even WWII combat aircraft, which had a fraction of modern airliner range (though it took a big dip once we went from props to jets), were able to travel to both Europe and Japan for duty.