Just wondering about the timeline of purchase and registration procedure .....

As I understand it from various posts and blogs on the interweb, getting a Certificate of Residence from Chang Wattana takes around 2 weeks, and is only valid for 30 days. Anybody with recent info to confirm or deny ? If that is right, just when do you need the certificate ? Initial ordering, at full payment and delivery, or when ? As a new car could take days, weeks or even months to deliver depending on options chosen and availability, getting a certificate too early could be a waste of time and effort if it is only valid for 30 days. But on the other hand I don't want the dealer to suddenly ring up and tell me to bring in the certificate tomorrow because the car has been delivered and is ready for registration !

Also some older blogs have mentioned using a Stat Dec/affidavit from your embassy as proof of address, but all the more recent stories I have read say Certificate of residence only. Anybody have recent info on this ?

Yes, usually valid for 30 days. The dealer needs it to register it in your name after the car has arrived at his dealership. So you should ask the dealer to inform you 2 weeks before your car arrives. If you had a yellow house book it would be easier, because you can always use it.