This might be a weird questions, but I really can't remember which way I did it last year. I remember I had to have my Embassy confirm my letter of overseas income and I also had the translation office change it from English to Thai, but I can't remember if:

1. First have the Embassy confirm the income and then translate that into Thai.

..or..

2. Have the income letter translated into Thai and then have the Embassy confirm the translation.

I am thinking the second one, because my Embassy says they can't confirm my income, as obviously they are not my employer and won't know if I will still receive the same funds next month. So they would be able to confirm the translation, which was enough for Immigration last year. But I want to be sure.

There is no requirement to translate into Thai for documents in English. But it appears you have a special Embassy that will not issue a normal income document but will issue a stamp on a translation so guess you had best do whatever you did last year - unfortunately it is not what others do so we can not tell you what you did last year.

Normal procedure is you visit Embassy and fill, or they fill, out a short document of your income and then they certify your signature (they may or may not check supporting documents). You present this letter to Immigration if in Thai or English without any need for translation.

Lopburi,

I had to get a translation of my income letter for Phibun Mangsahan Immigration Office in Jan of this year. I am a US citizen and it was a pain as the web site does not ask for the translation. I also had to show bank statements and ahow them where I had brought in more than 1M Baht in the last few months. They also wanted to see ATM receipts, I just showed then my US bank statement. It's a pain how the rules are written or translated and ask for this or that to verify income not everything on the list.

What extension were you asking for? Normally retirement is straight up but the family 40k income may have various interpretations from reports. That said some small offices do seem to vary from the norm.

Based on Marriage to a Thai national (female)

I must have had a black-out when I wrote this. I remember it now. First I need to get the translation of my employment letter, then have the Embassy certify the translation. That's what I did last year. And yes, they do want it in both Thai and English.