Why does my wife need to get our marriage certificate stamped for immigration in Thailand after 14 extensions?

My neighbours went back in October 2019, been here 12 years and were told the same had to be done for next time. As it happens they never got round to next time as the wife is still stuck in Russia!

My wife and I both from the U.K. had similar problems back in 2015.

We were married in Australia.

I was on an O-A Retirement and

My wife was on an O as my Dependant.

At our first annual extension Immigration would not accept our marriage certificate even though it was the original and embossed.

Written in English.

Had to go to Bangkok and get it certified as a true copy at the Australian Embassy translated in to Thai and then certified by Ministry of Foreign Affairs.

It meant an overnight stay in Bangkok.

We have to show these original documents every year when we do our annual extensions.

And what is the dept of consular affairs? Is it a thai gov't thing OR a brit consulate thing?

AFAIK (although this is for foreigners married to thaiz in the UK using the marriage certificate here it has to be sent back to Milton Keynes, then someone has to take it to the thai Consulate and THEN it has to be sent back here.

Again that might be a different situation (but I think any marriage cert from the UK is the same).

I took a pic of this at a copy/translation shop that caters to foreigner/thai marriages here

And you've gotten 14 years worth of previous extensions from Jomtien without any issue using a brit marriage certificate?