Volume 124 Issue 101 ง, Page 63-67, published on November 22 2007). That title translates to "Announcement of the Ministry of Information and Communication Technology about create and sell of group of stamps [with] emblems of provinces". And there's also a second one, Volume 125, Issue 61 ง, Pages 33-35 published on May 29 2008. These correspond to the first and second series of these stamps published in October 2007 and April 2008 as already featured here.The third series, which was apparently published last month, wasn't announced in the Gazette yet, but since the earlier series were also announced nearly two months after publication this does not mean anything.
By the way, the first day covers of the 3rd series are now online in the FDC blog - Pattani - Phayao, Phichit - Phrae.
Update: The announcement on the 3rd series is now published as well.