Dear Sangay lama,
We would like to inform that Nepal passport holders need visa to enter Viet Nam even you stay for a week
There are two fees you are required to pay: The stamping fee (paid directly at Vietnam's airport) + our service fee for the approval letter (paid in advance).
For instance, if you apply for the tourist visa with 1 month single entry, the service fee is 12USD/pax (paid online) and the stamping fee is 25USD/pax (paid in cash at the arrival airport)
Helen Truong (Ms.)