Wikipedia: Administrative divisions of Thailand: “Each of the provinces has one capital district (อำเภอเมือง, amphoe mueang), e.g. for Chiang Mai it’s Amphoe Mueang Chiang Mai. The exception is Ayutthaya Province, where both the province as well as the capital district have the full name Phra Nakhon Si Ayutthaya.”
This isn’t the case for Amphoe and Tambon. Some Amphoe have a Tambon and a capital with the same name. E.g. Ban Sida is in Tambon Sida which is in Amphoe Sida. Some Amphoe have a capital which is in a Tambon with another name. E.g. Kranuan is in Tambon Nong Ko which is in Amphoe Kranuan.