On SkyScraperCity, the posting from end of February says
เข้าอ่านใน KKL เห็นว่าจะมีการตั้งกิ่งอ.ใหม่ แต่ว่า เขายกเลิกไปแล้ว ก็คงจะต้องเป็นอำเภอเลย ก็ประมาณว่า อ.ภูคำน้อย (รวมหนองปอ สาวะถึ ภูคำน้อย ฯลฯ)The second one from Khon Kaen Link (maybe that is the acronym in the first posting) is basically the same contents
(I) read news that KKL planned to set up new minor district, but already abandoned the plan. When created, it would be Phu Kham Noi district (including Nong Bo, Sawathi, Phu Kham Noi etc.)
มีอ พสมช.พอจะทราบไหมครับ? เรื่องที่ขอจะจัดตั้งกิ่ง อ.ภูคำน้อย (รวมหนองปอ สาวะถึ ภูคำน้อย ฯลฯ)The answers in that forum don't add much, except that there are no more minor districts, so it'd have to be a full district.
As this area would have been split from Mueang Khon Kaen district, it would have made sense as Mueang Khon Kaen is 4th populous district of all Thailand with a population of 387279. Thus it would be easy to cover the population criteria for a new minor district, which is 30,000 citizen.
In older geocode lists, there already was an entry for Phu Kham Noi, which was supposed to get the code 4026 - this and two further planned districts were the reason why Wiang Kao did get the 4029, creating a strange hole in the district code table of Khon Kaen.
Thus it simply seems to me that that original poster has digged out the old proposal from 1997, when that minor district already was in the process of being created, but the process was halted due to the financial crisis. Since I haven't found anything else about this specific district, I don't think this one was restarted like Ban Chan, which became Galyani Vadhana district.
Sadly, all I know about these abandoned district proposals are the name and the code they were to receive, but not which subdistricts would be part of them - so in cases like Phu Kham Noi where the district name does not match any of the subdistricts I even have no idea where the seat of the administration was planned to reside.