Read the date, not only the rule
Most rules a reader is handed sound timeless, and this one is not. The country's place in the Hague Apostille Convention begins on 28 February 2027 and not a day sooner. A sentence about Thailand is therefore only half an answer until somebody attaches a day to it, which is why people come away with two conflicting stories.
So what you need for an apostille for Thailand has two answers rather than one, and two honest sources can still disagree. One was written for the position now and the other for the position from 28 February 2027. Work out which of those a note in your hand reflects before you act on it, and the contradiction dissolves.
Where Thailand stands today
Today an apostille for Thailand is not yet the certificate that closes a file, so document legalisation for Thailand still runs through a consular desk once the British stage is finished. From 28 February 2027 an apostille replaces that consular step, and the second desk disappears from the chain.
That makes an apostille from United Kingdom to Thailand a phrase whose meaning shifts on a day everyone can see in advance. There is also no apostille issued in Manchester for use in Thailand to be had over a counter, on either side of that day, because the mark comes from one central office by post.
The paper does not wait for the calendar
Whatever the date says, the sheet still has to exist and be readable. For births, marriages and deaths registered in the city, Manchester Register Office at Heron House, 47 Lloyd Street, Manchester M2 5LE issues certified copies, and it is that copy which travels, so the record you keep at home never has to.
The Legalisation Office (Foreign, Commonwealth & Development Office) then works on it by post from PO Box 6255, Milton Keynes MK10 1XX, charging £45 for each document by standard post. It keeps no public counter, in Manchester or anywhere else, so this part of the job happens through a letterbox.
Planning around a day you can see
A known day is far easier to plan around than a vague maybe. If the paper is wanted in Thailand before 28 February 2027, count on two desks, two charges and the waiting that a second stage adds. If it is wanted later, the job is shorter and cheaper. Deciding which of those two you are doing is the useful work on this page.