I had to get a new USA passport, I picked up the new passport yesterday at the Bangkok Embassy and was given this letter. I was told that must now go to Thai Immigration and transfer the entry stamp on my old passport to my new passport. I trekked up to the Immigration office close to Don Muang airport, took a ticket and patiently waited for 2 hours.

When my number was called, I passed over the letter from the US Embassy plus the completed form titled, “TRANSFER STAMP TO NEW PASSPORT”, I also passed over copies of my old and new passport, TM6 and entry stamps. 
The Immigration Officer then told me I do not need to transfer the entry stamp to my new passport, if I travel then I should simply present my old passport and new passport to the Immigration office at the border and there will be no problem.

I have a Non-O multi-entry visa based on marriage that expires on 31 October this year, my 90-day entry stamp is valid to 18 October this year.

I am a little perplexed about this because the Immigration Officer seemed to know what she was talking about.

I am also a little pissed because anyone who has been the Div. 1 Immigration will know what a pain it is first to get there and second wait for your number to be called.

I wonder why the US Embassy gave me this letter.

Has anyone else had the same experience?
 

They give that letter to everybody that get a new passport.

Many people do need to go to immigration to get their stamps transferred. People on extensions of stay have get them done there.

As you found out in your case it is not needed because it can be done at the airport.

I just wish I knew before, wasted a day ....