100 Baht - Rama VIII Series 6, Type I constitution watermark

Series 6 was issued under highly unstable conditions. Rama VIII — King Ananda Mahidol — was only a teenager residing in Switzerland during most of the Second World War, and Thailand had signed an alliance with Japan in late 1941 under considerable duress. The 100 Baht notes of this series were printed domestically by the Thai government after Allied bombing and blockades severed access to overseas security printers, a significant departure from the country's earlier reliance on Thomas De La Rue in London.

The Type I designation here refers to the constitution watermark — the Thai constitution book — distinguishing it from later watermark variants within the same series. Ananda Mahidol died under deeply disputed circumstances in June 1946, just as Series 6 notes were still in active circulation.