As found on the Panyathai wiki, the date August 10 was the date of the first election of a village headman. On this date in 1892, village and subdistrict headman in Bang Pa In district of modern-day Ayutthaya province were elected as a trial of the new thesaphiban administrative system. This system was officially introduced nation-wide with the local administration act of 1914. Sadly the text does not say when this date was announced as a remembrance day and celebrated every year since, however I was able to find an announcement in the Royal Gazette dating from 1989.
The word-file attached to the announcement I noticed at DOPA includes greetings from the various religious groups and also some ministerial officials. In detail the contributors are
- The Supreme Patriarch Nyanasamvara Suvaddhana (สมเด็จพระญาณสังวร)
- The chief of the Muslim in Thailand (จุฬาราชมนตรี), Sawat Sumalaisak (นายสวาสดิ์ สุมาลยศักดิ์)
- Chaovarat Chanweerakul (นายชวรัตน์ ชาญวีรกูล), Minister of the Interior
- Wichai Sikhwan (นายวิชัย ศรีขวัญ), Permanent Secretary for Interior
- Wongsak Sawatphanit (นายวงศ์ศักดิ์ สวัสดิ์พาณิชย์), Director-General of the Department of Provincial Administration