Vietnamese Citizens can apply online for their visa to Turkey.
You can apply here: TurkishVisa.com
Your e- visa will be valid for a total period of 180 days. Your stay cannot exceed 30 days, Single Entry.
Please note that the following rules apply:
Vietnamese citizens are required to travel with an airline company which signed a protocol with the Turkish Foreign Ministry.
At present, the airline companies that signed this protocol are Turkish Airlines and Pegasus Airlines.