From Thailand, visitors can apply for a visa through one of the embassy of Vietnam in Thailand below or apply for a Vietnam visa  online. Here below is the specific address of Vietnam Embassy you may concern:

Embassy of Vietnam in Thailand 

83/1 Wireless Road, Lumpini, Pathumwan, Bangkok 10330, Thailand
Tel: (662) 267 9602
Fax: (662) 254 4630 Consular:  251 7201, 250 7525

Consulate General of Vietnam in Khonkaen – Thailand
65/6 Chatapadung, Khonkaen 40000, Thailand
Tel: (66) 4324 2190
Fax: (66) 4324 1154

Besides, citizens in Thailand can select among 3 options to get visa to Vietnam:

–          Visit Vietnam Embassy in Thailand or in any other countries to get Vietnam visa done there.

–          Apply for Vietnam visa on arrival at https://vietnamvisaonentry.com/apply-online/ and pick up your visa at one of 3 international airports in Vietnam

–          Apply for Vietnam visa code at https://vietnamvisaonentry.com/apply-online/ and get visa stamped at Vietnam Embassy where you wish to pay a visit to.