I've had my UK passport legalised in the UK - they do this with a certified copy and return it to you with the apostille attached to the back. I've arrived on a non O visa and I will now get it translated in Bangkok and take to MFA for the translations to be certified but someone has told me I have to get something done at the UK embassy first but I've no idea what! Can some one advise please?

Did it all back in April, you need an Affirmation of free to marry certificate from the embassy which you also need to get translated to Thai and then certified by the MFA. You might also need to get your passport confirmed as genuine depending on what your marriage office requires.

None of this is needed if you're extending a 'Non Imm O' visa based on marriage.

59 minutes ago, poppysdad said:

Did it all back in April, you need an Affirmation of free to marry certificate from the embassy which you also need to get translated to Thai and then certified by the MFA. You might also need to get your passport confirmed as genuine depending on what your marriage office requires.

He is applying for a extension of stay based upon marriage. He not preparing to register his marriage at a Amphoe.

1 hour ago, Jaggg88 said:

've had my UK passport legalised in the UK - they do this with a certified copy and return it to you with the apostille attached to the back. I've arrived on a non O visa and I will now get it translated in Bangkok and take to MFA for the translations to be certified but someone has told me I have to get something done at the UK embassy first but I've no idea what! Can some one advise please?

What are you doing that requires your passport to be legalized?

The UK embassy here can do it as well.

4 hours ago, ubonjoe said:

What are you doing that requires your passport to be legalized?

The UK embassy here can do it as well.

I'm applying for an extension based on marriage. I thought I had to get my passport legalised and translated. 

Do a Google search for Non Imm 'O' visa extension requirements. You should find all your answers.

Oh sorry the legalisation is for the company I'm going to work for here in Thailand. I thought they meant for my marriage extension.

10 hours ago, Jaggg88 said:

Oh sorry the legalisation is for the company I'm going to work for here in Thailand. I thought they meant for my marriage extension.

I have never heard of any company wanting a passport be legalized. Maybe translated but not that.

I think the legalization by the UK government will be enough. The translation would them be certified here.

In over 40 years of working, and later living in retirement, in Thailand I have never been asked for any form of 'legalisation' of my UK passport/passports. However, I married my Thai wife in Taiwan and had the marriage certificate approved and stamped by the Thai embassy in Hong Kong, which was accepted in Thailand by the Thai immigration authority when applying for an annual extension based on marriage. The validity of my UK passport has never once been questioned during these procedures.