I will return to Chiangmai for selling my car to my friend, but I don't know the detailed process, can anyone share with me about the experience and what documents should my friend and I bring?

If I need certificate of residence, how can I get it on next day?

As I will stay in a hotel for only one week (the main purpose of my return to Thailand is to sell my car), I don't have a long term rental contract with owner. Can I successfully get a short term rental contract with hotel or hostel, the owner agree or disagree, any experience?

Thank you!

You can normally get one from your Embassy or consulate. If no consulate in Chiangmai. stop over i Bangkok at your Embassy to get one.

In your case getting the certificate of Residence you really only have 2 choices

1- Your consulate in Chiang Mai ex: US Consulate (you did not state your nationality) is $50 or 1750 baht ( US Consulate available Tuesdays & Thursdays)

2- The GT guys next door to Promenade Immigration office do it for 600 baht or about $17 USD ready next day

Both are basically no hassle deals so not to worry about where your staying contracts etc.

Just state where your staying ...Consulate you just swear it...GT does not care & just asks...

GT does include a photo in their 600 baht deal

You will definitely need a rental contract or ownership papers of a property for a resident certificate.. An associate of mine tried in vain to use a long term hotel booking...(12 months +) That was in Phuket as I remember but maybe different in other provinces... The actual transfer at the Transport office was as he put it 'the ball ache'... Good luck

Go to Expat Autos (on the internet). Honest guys, American, and even if you have to leave before the car is sold, they'll see everything is done properly.

They handled the sale of my car, and no problems at all.