Checked in to Tiger Airways was handled by Vietnam Airlines staff. The print out of the confirmation email of the reservation was needed here. The process was fast and smooth, and the Vietnam Airlines staffs were very friendly.
However, international departure from Noi Bai airport will be levied USD $14 Ve Thu Phuc Vu Hanh Khach, or in English Passenger Service Charge. It was in essence departure tax, which I thought was very expensive.