As a part of ASEAN, Laos citizens are exempt from Vietnam visa for 30 days. For stay of longer than 30 days, Laotian nationals may have 2 options: Visit Vietnam embassy in Laos or apply for a visa on arrival to Vietnam from Laos online. Laotian citizens may apply for both tourist and business visa to Vietnam for the stay of 1 to 6 months from Laos. Please check this link for visa fee for Laotian citizens.

All the information for getting a visa from Vietnam embassy in Laos can be found here: http://www.mofa.gov.vn/vnemb.la