The answer to the question, "Do bean thread noodles need to be soaked,?" is that it all depends on how the noodles are going to be cooked. For soups and stir-fries, soften the bean thread noodles by soaking in hot water for about 15 minutes. Drain and use as called for in the recipe.
However, another popular way to serve these noodles is to deep-fry them in hot oil. In that case, the noodles should not be soaked or blanched first - just add the dry noodles into the hot oil. Then watch them puff up and turn a deep golden brown!
In any case, whether you're deep-frying or stir-frying, cutting the mung bean noodles cross-wise ahead of time will make them easier to manage.