Many Thai Embassies/Thai Consulates do have a disclaimer/notice to Not Submit an Application Too Early before planned/intended travel dates, regardless of the type and duration of the Thai E–Visa
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Do not apply for a visa earlier than 90 days before you arrive in Thailand. (The best time to apply for a visa is approximately 4 weeks before the departure date.)
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VISA PROCESSING TIME: 5-7 WORKING DAYS (UP TO 14 WORKING DAYS DURING HIGH SEASON)
Applicants are recommended to apply for the visa in advance at least a minimum of 2 weeks but not later than 10 weeks before the expected date of arrival.
Do not apply for a visa earlier than 90 days before you arrive in Thailand. (The best time to apply for a visa is approximately 4 weeks before the departure date.)
Unfortunately, you applied "too early" with the Thai Embassy in London for your Multiple Entry Tourist E–Visa, because they promptly processed your application and issued you a Multiple Entry Tourist E–Visa in early September (10 September 2025):
So, if you had applied a bit later, say this month (October 2025), then you would have seen your E–Visa Validity Dates that you had suggested....
Regardless, do understand the particular details and differences between Visa Validity and Period of Stay....
Upon receiving your application, it takes within 10 working days to get your visa (the processing begins after we receive your required documents). The processing time can take longer in certain cases.
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FYI— Monday, 13 October 2025 was a Public Holiday for the Thai Embassy in London and also in Thailand