Gen Boonlert, chairman of the pre-cadet school's Class 1, on Thursday called for military officers who are junior, including those on active duty, to support the PDRC's campaign for reform.
He claimed to represent the elderly, now senior, students of Classes 1-9.
Pol Maj Gen Monthien Prateepavanich, a member of Class 8, led about 25 alumni of Classes 7-13 and Class 19 to a press conference, where they declared that Gen Boonlert had acted without consent from all the former students he claimed to represent.
Since a royal decree had been issued to dissolve the House of Representatives and a general election scheduled for Feb 2, Gen Boonlert and his followers had acted improperly in calling for support for the PDRC, which is trying to block the elections, he said.
"We do not agree with Gen Boonlert and his supporters. We would like to call for all old students of the Armed Forces Academies Preparatory School to comply with the royal command so that the Feb 2, 2014 election can be successfully held," Pol Maj Gen Monthien said.
An informed source said the Defence Ministry has asked all political groups not to claim to represent any of the armed forces or military institutions.
Gen Boonlert led the unsuccessful anti-government protests by the Pitak Siam group.
The Armed Forces Academies Preparatory School was established in 1958, and class numbers date from then. It provides education equivalent to the last three years of senior high school and is run by the Royal Thai Armed Forces Headquarters. Most graduates move on to the professional academies, such as the Chulachomklao Royal Military Academy, the Royal Thai Naval Academy, the Royal Thai Air Force Academy and the Royal Thai Police Academy.