@Rob ******
from Chiang Mai it is probably easiest to visit the Thai embassy in Vientiane, to apply for a 60 days tourist visa single entry. The requirements are absolutely doable (contrary to absolutely shitty requirements in Penang, Hanoi or Ho Chi Minh), however you will need an appointment with the embassy, and they require 3-4 working days for the processing. Here is the relevant webpage of the Vientiane Embassy
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