From Indonesia, you may apply for a visa to Vietnam either through Vietnamese embassy in Jakarta or apply for a visa on arrival.
Visa on arrival - Visa at Embassy of Vietnam In Jakarta, Indonesia
Embassy of Vietnam in Jakarta, Indonesia
Jalan Teuka Umar 25, Jakarta Pusat
Phone: (21) 3100357/8/9
Fax: (21) 3100359 or 3149615
From other travelers experience, people apply for a visa in Jakarta used to face 2-3 days waiting and a cost of $120 for the same visa.