While looking though the "interesting articles" section of the website of the Department of Local Administration (DOLA), I stumbled on one which was titled สาร รัฐมนตรีว่าการกระทรวงมหาดไทย เนื่องใน "วันเทศบาล" วันที่ 24 เมษายน พุทธศักราช 2550 (Speech of the Minister of Interior on the Municipality Day April 24 2007). Now just few months ago I wrote about the newly introduced "Day of Local Administration" which includes the municipalities as well, so I was a bit surprised to see that the municipalities now have two commemorative days.
The Municipality Day (วันเทศบาล) was introduced in 1990, at least in was officially announced in the Royal Gazette in September 1989. If I read the text of this announcement correctly it does not give the rationale for choosing this date, but I can suggest a very likely explanation - on April 24 1934 the first Thesaban Act was promulgated by publishing it in the Royal Gazette.
So yet another entry in my Google Calendar, so I won't miss any official celebration of this kind in case I am in Thailand on any such special days.