I read from other posts that immigration will transfer to the new passport the extension to stay stamp( 1 year in my case) and the entry stamp.

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I THINK I also read that rather than having to show both the old and new passports in future extension ,that although immigration cannot transfer the original visa they can put in the new one a note of the original visa number....and so negate the need for producing both passports.

Was I dreaming? or is this the case?

If you are on extension of stay they transfer your permission to stay stamp and there is another stamp which references your previous PP number and visa.....literally takes 15 minutes to do this and is free

Yes, they note the original passport number, the vise type, and the last date of entry in the new passport.

If there was less than a year validity when you renewed your visa, they would only extend until the passport expired. But, when you transfer information, they add the missing time so that, in the end, you do get the full year extension.

Yes, they note the original passport number, the vise type, and the last date of entry in the new passport...

...and a copy of your extension stamp.

In Pattaya I went along in the afternoon, handed in my new and old passport and returned the next morning to collect them. No charge involved!