btw, Andrew has some comments here although disagree with him over the influence of the US military.
Steven P. Sciacchitano and John M. Cole Jr, two former US military officers who are Thai specialists and served at the US Embassy in Bangkok, have an op-ed in the Washington Post entitled “Why Thais still fear Thaksin Shinawatra”. Key excerpt:
Thaksin asserted that since he was a moral person and a successful executive, he had the best claim to govern Thailand, and that the opposition was illegitimate.  Over time, more Thais saw in his actions evidence that he was using his office and his enormous personal wealth to gut the constitutional reforms of any real meaning and to perpetuate himself in power. This was the main reason for the conflict between Thaksin and his opponents, not the desire of a pampered elite in Bangkok to maintain its privileges.  In 2006, after Thaksin tried to manipulate the army promotion list, installing loyalists in key command positions to further his reelection prospects, the army acted to remove him.
This is not an apology for the 2006 coup; reasonable people disagree over the extent to which perceptions of Thaksin’s ultimate goals were justified. Some of his most committed critics opposed the coup, while others supported it as the lesser of two evils. It’s not hard to sympathize with the hope of many Pheu Thai supporters for a fairer society, but stability in Thailand depends not just on accepting the results of the recent election but also on whether Pheu Thai can separate itself from Thaksin’s personal interests. Unfortunately, all indications are that he still controls the party from exile in Dubai, and as long as this is the case, the situation remains very dangerous.
BP: On , BP would agree that for many people who opposed Thaksin that it was because of how he acted, particularly post-2005 and that they saw he was corrupt and beyond the law and this was part of the reason for the conflict. As Pasuk Phongpaichit argued in “Thai politics beyond the 2006 coup” (PDF):
The middle class initially welcomed Thaksin in 2001 as a leader to continue the modernisation reforms begun in the 1990s. Their support held up for four years, but in 2005, they turned against him in a violent and highly emotional way.
The middle class had three fears: first, that it was dangerous to have a state dominated by a clique of the biggest and rather corrupt business interests; second, that they would have to pay for Thaksin’s populism through increased taxes and the resulting economic disorder; and third, that Thaksin’s formula – an alliance of big money and big numbers – would make the middle class politically irrelevant.
But as Pasuk also noted:
In 2006, Bangkok again felt threatened, but this time by a political leader and political party which had built unprecedented support in the rural areas of the North and the Northeast by delivering a range of populist programmes, and promising more.
Thongchai Winichakul, a veteran of the student movement in the 1970s and now a professor of history at the University of Wisconsin, put it this way: “This coup is not only for toppling Thaksin. It is a royalist coup with a purpose. If one is not so naïve, Prem’s fingerprints and footprints are all over the place for us to see” (Thongchai 2006a: 6). According to Thongchai (ibid.), the purpose of the coup—abstracting somewhat from the detailed conditions leading to the event—was to make sure that “a government that is obedient, even submissive, to royalist leadership” is in place in case of succession.
BP: So yes, there is the Thaksin was corrupt element, but the coup would never happened just because of that. The establishment also felt threatened by Thaksin and that he was sharing in the spoils that they had…
For , the official reasons for the coup were:
We agreed that the caretaker prime minister has caused an unprecedented rift in society, widespread corruption, nepotism, and interfered in independent agencies, crippling them so they cannot function. If the caretaker government is allowed to govern it will hurt the country. They have also repeatedly insulted the king. Thus the council needed to seize power to control the situation, to restore normalcy and to create unity as soon as possible.
BP: After the coup, coup leader Gen. Sonthi said the coup was staged because there was a lot of vote-buying in the previous election. A former senior military officer and member of the coup-appointed parliament said it was because Thaksin had underspent on defence spending. Now, it is certainly correct that military officers feared for their future as per a journal article entitled “THE THAI MILITARY: A POLITICAL ROLE”:
A number of senior officers issued official complaints alleging government interference in reshuffling processes in July 2006. This was around the time when Thaksin was reported to have held a private meeting with former Class 10 officers, an action that was met with strong suspicion within the Army. (Lee 2006) Several of Thaksin’s former classmates were expected to receive promotions in the reshuffling of October 2006. In fact, it was widely speculated that the coming round, which the coup conveniently pre-empted, would remove Sonthi and his supporters once and for all. (Beech 2006).
BP: On that July reshuffle, it was as Michael Nelson notes Gen. Sonthi who was removing Thaksin’s people:
Shortly afterwards, Army Commander Sonthi deprived Thaksin’s classmates from the Armed Forces Academy’s Preparatory Class 10 of much of their operational military power by transferring many of their trusted middle-ranking officers to other positions. A commentator in the Bangkok Post (July 21, 2006) had this to say: “The latest military reshuffle serves as an unmistaken message to Mr. Thaksin and his ex-classmates at the pre-cadet school that Gen. Sonthi’s first and foremost loyalty is not to them.” Prem continued to drum up support for his views of the role of the military vis-à-vis the political leaders. On July 28, he gave a special lecture to 350 cadets at the Naval Academy, stressing that national leaders must be ethical and have a high degree of morality:
BP: Isn’t it rather odd to criticize a civilian leader of manipulating the selection of military officers given that the military had themselves removed most of the Thaksin loyalists in advance of the coup. That Thaksin was going to put some of his people back into place and to possibly remove the army chief is called “manipulation”. One wonders what the military officers would think if Obama wanted to choose his own generals or what they think should happen to a general who had publicly shown disrespect to Obama and his administration. Oh wait, we know what would happen. On “political meddling/manipulation”, here is what BP said in a previous post:
So it is political meddling when the PM chooses who he/she wants for the Army C-in-C position, but it is professionalism when military leaders appoint people to key positions to protect their own interests. Only, The Nation cannot see the contradiction.
Or this other post:
References to the “politicization of the military” under Thaksin actually means removal of Prem’s role in the choice of the Army C-in-C and other members of the brass and the PM choosing the Army C-in-C. Ultimately, someone has to choose the Army C-in-C.
BP: BP is a little skeptical that the military officers were helping Thaksin in his reelection bid – contrast with the 2007 general election where the military were heavily involved against Thaksin – this is what the Interior Ministry were for, but putting key people in military positions was more about preventing a coup….