Your Thai friend should be a wealth of information, ask them.
Chiang Rai airport is about 20 minutes away from Chiang Rai. Not the busiest but maybe 6 flights a day. Domestic flights are good and relatively reliable
It's actually a pain in the rear for companies to do this. When they did mine in Chiang mai, it was over 400 pages of documents. Immigration also wanted originals or everything so 800 pages.
Took 2 staff 2 weeks to prepare. Immigration also went to my work place and asked each and every worker, all 89, if I actually worked there.