If the Saudi Arabian passport holders want to apply visa at Vietnam Embassy, they should to know that:
Visa administrative Institution: Vietnam Embassy
Processing time: depends on you how fast you need. But for sure, you should make a call to Vietnam Embassy for details.
Required Documents: passport, money and 1 new envelope with stamp on it and your exact home address in order to avoid losing issues.
How to apply: please take a look at contact information of Vietnam Embassy below
EMBASSY OF VIETNAM IN RIYADH, KINGDOM OF SAUDI ARABIA
Address: Villa No. 23 Al-Dhiyafah Street, Al-Nuzha District, Riyadh, Kingdom of Saudi Arabia
Phone: +966-1-4547887 ; +966 -1-4569756
Email: firstname.lastname@example.org | email@example.com