Steps 2-3-4 I completed all without leaving where I live now, because I mailed the documents. 🙂

Is your marriage certificate from Florida? Then it looks like you would want this for step 2:

And for step 3, you want this:

For step 4, was the document issued in Florida? If so, you would be served by the Royal Thai Embassy in Washington DC:

See here for information on legalization of documents:

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@Sunida *************

It's a lot of steps and takes a while, but it can be done. 🙂 Although I don't know if you are in the US right now or in Thailand. If already in Thailand...I imagine it would be very difficult and take a very long time, even if just because of how long it would take to mail between Thailand and the US multiple times. But if you are in the US where it would be easier and quicker (although it still takes months), and if you still would like to try, you can reach out anytime for tips and help on going through those steps.

@Sunida *************

I think there is a definition mismatch. You were told "notary" or "notarized", but what I think you need is the full authentication/legalization process for your marriage certificate.

As Pom Argent mentioned in an earlier reply, the process is as:

Step 1. Obtain certified copy of the marriage certificate from the county where you were married in the US

Step 2. Have that authenticated by the Secretary of State in the US state where you were married.

Step 3. Have that authenticated by the US State Department in Washington DC. They will not do so if step 2 has not been done.

Step 4. Have that authenticated by the Thai Embassy or Consulate that serves your region in the US. They will not do so if step 3 has not been done.

Step 5. Get a certified translation into Thai of the entire document stack above.

Step 6. Have all that approved by the Ministry of Foreign Affairs in Thailand

Step 7. Take all of the above to a local Amphur in Thailand to have your family status updated to show that you two are married. They will give you the Kor Ror 22 form.

The US embassy in Thailand, as far as I know, does not offer such document authentication/legalization services, such as authenticating a marriage certificate that has been authenticated by a US state. Document authentication/legalization is different from notarization. I think that is where some of the confusion is coming from.