Last time, Ms Tho is the interpreter. She is my friend's wife, so the price was good and the time is flexible. This time, maybe the price will higher (around 100$/day) and they will ask for their schedule. So if you have detail plan: the arrival and departure time at Tan Son Nhat airport, what do you want to do for each day at our factory, it will be good for finding an interpreter. Because I think maybe you won't need them for the whole time you are here.
あなたが滞在中ずっと通訳が必要ではないように思うからです。