I had a Gov. UK. Daily Update in my email this afternoon, which is subtitled;

'From 1 January 2019, the British Embassy Bangkok will no longer be providing British Nationals with letters confirming their income.'

This letter has previously served as a supporting document for obtaining a Thai retirement or marriage visa. The British Embassy Bangkok is stopping the certification of income letters because it is unable to fulfil the Thai authorities’ requirements to verify the income of British Nationals.

British Nationals should now demonstrate that they have an amount of at least 800,000 THB in an account in Thailand for no less than three months prior to the visa application, or a monthly income of at least 65,000 THB transferred into an account in Thailand for a retirement visa. For a marriage visa, the amounts are 400,000 THB in an account in Thailand for no less than three months prior to the visa application, or a monthly income of at least 40,000 THB transferred into an account in Thailand. A bank statement should be used as the supporting document for obtaining a Thai retirement or marriage visa.

All British Nationals concerned should note that the last date for income letter applications is 12 December 2018.

I note that this mentions the Visa and not specifically Visa Extension so I tried the Further info: https://www.immigration.go.th/content/service_18 but the immigration page says 'Not found'. Does anyone on the forum have more info?

Gov.UK page @https://www.gov.uk/government/news/british-embassy-bangkok-to-stop-certification-of-income-letters?utm_source=665424a0-f53b-4a18-ad69-d8d1a7fdda1f&utm_medium=email&utm_campaign=govuk-notifications&utm_content=daily

On going topic about it, This one