My search of ThaiVisa for registration of foreign marriage led me to this post written by thainet 18 months ago:

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But to make a one year extension based on marriage, they require the following.

1)Original marriage certificate from your home country 

2)Translation of that certificate into Thai

(both of the above documents MUST be stamped/certified by your Embassy in Bangkok)

3)The MFA will issue a document certifying 1) and 2) above. (Kor Ror 22)

 

This is enough to get your first extension.

Starting from your 2nd extension you will need all of the above PLUS the updated RK22 from your local amphur to prove you are still married.

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At this point we (Thai wife and I) have only an official certified copy of our 1999 US marriage certificate issued by Clark County in Nevada.

 

Can the above steps all be completed using translators, the US Consulate in CM and a branch of the MFA in CM?

Is there a local amphoe that will cooperate and issue the Kor Ror 22?

 

You should be able to get the marriage certification at the USA consulate in CM and the Thai certification of translation for the marriage certificate done at the CM passport office. I can't answer if the CM immigration requires that be done in Bangkok.  

Star Visa company near the US Consulate are experts at making this all legal and easy for you.  

Don't see an edit function above so:

Star Visa are experts in assisting you in making this an easy process with MFA and US Consulate.

Thanks for all the assistance.  We just arrived and I am planning on getting a 60-day extension to allow bank deposit to "ripen" before seeking the one year extension around end of January.

I just did this.

 

1) Get original marriage certificate from the US. No one really checks this and a copy might even be good enough.

2) Go to US consulate or embassy and sign an Affidavit that says you are married. Get a certified copy of your passport bio page as well.

3) Get the two documents above translated and certified by MFA. I paid a visa agent for this part.

3) Go to Ampur in Chiang Mai with the documents above and register your marriage. We received the Kor Ror 2.2 right then.

 

Feel free to PM with any questions. I just did all of this 2 weeks ago in Chiang Mai.

 

-Bryan