Register Used Car in Different Province from Bought

I am buying a used car from a farang resident in Pattaya and will register it in my wife's name.  My wife & I live in Chiang Mai most of year & our / her house registration ref blue book is Chiang Mai.  We will visit Jomtien in March to pick up car & stay at a condo I own while there. 

My questions relate to ensuring that we have all required paperwork / signatures etc before returning to Chiang Mai & be told at CM transport office that something is missing and the seller (a resident of Pattaya) may have to appear for some reason (signatures in right document / location, etc whatever).  Thanks in advance for your suggestions.

1. I doubt this is the case, but want to ask: If my wife takes her Chiang Mai blue book house registration with her to Pattaya can she go to Pattaya transport office with the seller to register the car, either as a Chiang Mai or as a ChonBuri registered vehicle?

I intend to at least visit one of Pattaya's commercial satellite registration locations to ask what exactly is required but am suspect of advise a disinterested person may provide. 

2.  If she cannot do #1, what do you suggest we do to ensure that all required paperwork (for example, to include sellers correct signature on proxy document) is included and signed in proper locations prior to leaving Pattaya to return to Chiang Mai?