Hi, I searched the forum and found conflicting info so would very much appreciate if somebody could share first-hand info on what kind of documents I need in Chiang Mai to SELL a motorbike with the green book in my name? 

More specific: do I as the seller need a Residence Certificate to transfer the bike to the buyer?

Yes, you'll need a Residence Certificate if you don't have a yellow house book or WP and you'll need your passport with valid visa/extension. It's best to go to the DLT with the buyer to make sure the bike is registered in their name. I've done it before and it took a couple of hours at the DLT.

 

Here's a thread from a couple of years ago that should be of help.  

 

It seems the above link to another TV thread is not working. I found it by google though.  

copy and past from my notes

 

Thai seller needs to supply
Signed copy of  ID card  front and back ( not expired )
Signed copy of house registration ( not allways required )
signed  " nungsue moub umnart "   หนังสือมอบอำนาจ ( if seller is not going with you to DLT )
signed  "beb  kum kor own le rup own "  แบบคำขอโอนและรับโอน    ขส.บ. ท. - 11
green/ blue book signed by current owner

 

Foreigner seller needs to supply
certificate of residence from immigration ( should be free at immigration but varies from place to place )
For foreign seller, instead of certificate of residence also work permit or yellow housebook is accepted.
if foreign seller has left Thailand then a signed copy of the exit from Thailand stamp in their passport instead of residence certificate and valid visa stamp.
(Certificate of residence not required in all provinces ?    / DLT's Pattaya requires it )
sometimes the police station will give you this document too.
copy passport photo page
copy of visa page and or extension  ( not expired )
signed  " nungsue moub umnart "  หนังสือมอบอำนาจ ( if seller is not going with you to DLT )
signed  "beb  kum kor own le rup own "  แบบคำขอโอนและรับโอน    ขส.บ. ท. - 11 ( if seller is not going with you to DLT )
green/blue book signed by current owner

So list of provinces where residence certificate is required ( from foreign seller ) so far is
Chonburi/Pattaya
Nakhornratchasima/Korat
Khon Kaen  ??
Buriram for sure
Chiang Mai ?