If you are just transferring the extension from your old passport to your new one, you take the embassy letter to immigration, with your new passport, and they will take it from there.
I will ask at the Chiang Rai office and point out the police order and their own instructions which says “two months”...nothing else, just two months. Thanks
For the extension in Chiang Rai they require the following: Tm7 application form + 1 photo
Passport and copy
Visa page copy ,Tm6 entry card in passport,copy wife ID card, copy Wife housebook, copy Marriage certificate, copy Kor ror 2 form - can be obtained at the Amphoe office for 20, baht 1900 baht