Only little bit over one month ago, in the meeting 43/2010 of board one to consider draft laws, the merge of the subdistrict administrative organization (TAO, องค์การบริหารส่วนตำบลวังน้ำเย็น) and the subdistrict municipality Wang Nam Yen (เทศบาลตำบลวังน้ำเย็น) was approved, now the corresponding announcement was published in the Royal Gazette. Sadly the announcement does not state the date this merger becomes effective, so I can only guess it has already happened between the board meeting and the Gazette publication.
The municipality, which was created as a sanitary district in 1980 originally only covered a rectangular area around the main highway as one can see in the map enclosed in the Gazette announcement of the sanitary district creation. The TAO was created in 1995 by upgrading the Tambon Council, and it covered the remaining area of the subdistrict Wang Nam Yen, thus completely encircled the municipality. Sadly this is about all I know about the TAO, their website has already expired, but even when it was still running it had not much information anyway - especially sad that their emblem was not depicted anywhere, nor the location of their office was shown. The map within the current announcement shows several placemarks including the location of the municipality office, but does not list the former TAO office.
Another interesting detail about the municipality is that their mayor Wanchai Narirak (นายวันชัย นารีรักษ์) was already the first elected chairman of the sanitary district in 1994. It's not clear whether he won all the elections in the meantime as well, though I think it is quite likely.