I'm planning to remarry a Thai national who I divorced a few years ago.

 

I need to obtain an affirmation to marriage for the new marriage from the UK embassy.

 

The original marriage at the amphur office in Thailand was never registered at the UK embassy. I guess they would be unaware of this marriage.

 

Do I need to provide evidence of the Thai divorce? If yes, do I need to translate and have it notarized by the Ministry of Foreign Affairs? If not, I can save myself lots of paperwork.

You will not be able to get married without an affirmation to marry translated into Thai and stamped by the MFA. That is fact.

I guess what you are asking is will you be able to get away with lying to the Embassy.......well I guess if you wish to swear that you have never been married before and then sign your name to it then the Embassy will probably issue your letter but then what happens when the Thai computer system throws out your previous marriage details and you are found out?????

HL

First of all, as I understand it, there was no requirement to register a divorce with the British Embassy, l further understand that there is no facility to do so anyway.
You're right, and happylarry has confirmed, that you need to get an affirmation of freedom to marry from your Embassy.
You will need to provide evidence of your divorce to the Embassy to be able to swear the affirmation that you're free to marry. Your evidence of divorce needs to be translated into English, then the translation company will need to certify their translation, which they do as a matter of course, it doesn't need to be signed off by the MFA, though the affirmation will.
Even though the Consular staff are Thai, they will still want the evidence of your Thai divorce translated.
I don't see where you need to lie.