To travel from Chiang Mai to the Thai Embassy in Laos, consider taking an early flight to Udon Thani, then use a mini van to reach the Nong Khai border. After crossing the border, you can find transportation to the Thai consulate in Vientiane. Alternatively, there are options like mini buses, taxis, and motorbikes for different segments of the journey.
Buy an overnight bus ticket at Arcade busstation in Chiang Mai to Nong Khai (border) Bus drops you at the Nong Khai busstation in the morning. (Some busdrivers are willing to drop you at the borderstation) if not: take Motosai taxi to the border. Cross the border into Laos. Take a minivan to Vientiane Consulate. Arrive there around 9-11 am. Apply for visa. Go back next day afternoon and pick up visa. Then go back the same way. Cheapest and easiest solution.
, you aren't going to be the ONLY foreigners going to the thai consulate in Vientiane. Follow the herd, there will be a LOT of them at the border crossing into Lao.
OR find a visa run company up in Chiang Mai that takes you.
Koko ******
ORIGINAL POSTER
But now I can't find the transport service chiang mai to Vientiane Thai consulate. Because my friend, she's the first time to apply the ED visa in other country.