Thai banknote are always change in design by series. The first bunch of Thai banknotes were printed from Messrs Thomas de la Rue & Company Limited in England. In 1939, Bank of Thailand (BOT) was established and took over the responsibilities in monetary policy and currency control.
In WWII, due to the Thai Government allied itself to with Japan, the British printing company could not supply banknotes to the Axis, so Thai government requested the Japan government to print banknotes in 5th series.
Anyway the banknote transportations always were attacked by the Allied, Thai government assigned The Royal Thai Survey Department (RTSD) to print banknotes by using local raw materials. Because of the remained high demand of banknotes, BOT also commissioned the Naval Hydrographic Department (NHD) to carry out additional printing. [more]