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

All the information for getting a visa from Vietnam embassy in Brunei can be found here:http://www.vietnamembassy-Brunei.org/