A report by a bipartisan US task force on interrogation and torture of al-Qaeda suspects after the Sept 11 attacks presents the most complete picture yet of Thailand's covert role in the process.
But "The Report on Detainee Treatment" by The Constitution Project think-tank leaves many questions unanswered about what happened behind the scenes between 2001 and 2003, when the US Central Intelligence Agency cleaned and closed up its secret interrogation centre in Thailand.
The 16-year-old Constitution Project mined more than 2,500 public and classified documents in the most comprehensive report yet of how al-Qaeda members and suspects were found, fixed, captured, incarcerated, interrogated - and sometimes tortured - after the attacks on New York and Washington in September, 2001.
It has 25 references and a specific chapter on Thailand, all of which fail to answer key questions.
The report, authored by members of both major US political parties, concluded after a two-year investigation that, "It is indisputable that the United States engaged in the practice of torture".
It also concluded that some of that torture took place at a facility in Thailand set up and staffed by the CIA. But while it is more forthright than many government reports of the past, including a well-known compilation by the European Union, it fails to advance the issue.
The US government has refused to provide any details about the "safe house" interrogation centre where al-Qaeda members were waterboarded.
Every Thai government involved - from Thaksin Shinawatra who was in power at the time, to Prime Minister Yingluck Shinawatra today - has simply denied the presence of any such CIA facility. Military and national security spokesmen have slavishly adopted the same line.
The US report by the Constitution Project makes it clear there was such a facility and torture took place. It confirms that some previous speculation was factual. But disappointingly, it fails to move the story, or provide new facts.
Among the questions still unanswered:
• Who approved the CIA interrogation facility in the first place?
It has long been assumed Thaksin himself made the decision to provide "any help we can" to the US, including the CIA. No official or report ever has confirmed that.
• Where was the facility?
Like other reports, including newspaper articles, the latest Detainee Report speculates but cannot confirm. The old story of a facility at or near the Udon Thani Royal Thai Air Force base is repeated.
One interrogator let slip several years ago that he had to take an up-country flight from Don Mueang International airport to reach the interrogation base. And a prisoner told the International Red Cross it was a "very primitive place with a snake problem".
• What was the role of the Thai security establishment?
The facile answer is "probably nothing". The real answer is likely to be more interesting.
From 2001 to 2003, when the CIA facility was being planned and then used, the "war on terror" was a serious and worldwide subject. Then-president George W Bush was about to make Thailand a "Major Non-Nato Ally". A rebellion was brewing in the deep South, with operatives trained by al-Qaeda in and near Thailand.
The report, strangely, concludes purely on speculation that the separatist violence in the South probably led the US to ask Thailand for permission to torture al-Qaeda suspects on Thai soil.
Unfortunately, it warps the time line out of kilter to do that, and loses credibility. The Constitution Project claims "Thaksin Shinawatra's suppressive policies towards the Muslim South triggered violent riots" that led to Thailand being receptive to a CIA interrogation facility.
In fact such unrest occurred after the CIA had used and already closed its safe house.
The report seems on safer ground with general speculation there were "positive, long-standing relationship(s) between the CIA and Thai intelligence counterparts built during the Vietnam War and its aftermath".
If anything, the report builds on the extreme conspiracy theory that the US was involved in events in the deep South of Thailand.
The question of "why" Thaksin and Thailand allowed the CIA to interrogate al-Qaeda prisoners and suspects has never been a serious mystery. In mostly popular decisions, Thailand openly aided the US in preparations for its invasions of Afghanistan in 2001 and Iraq two years later - and Thai troops served under US command in both countries.
The report skirts or repeats old speculation on more important questions: "Where" was the base (or perhaps two bases, according to some reports)?; "what" did Thailand receive?; "who" from Thai military and intelligence circles was involved?
The report is 560 pages, but much of that is taken up by references and an index. It is literally repetitive in parts, with entire pages and paragraphs included twice or more.
A 4MB PDF version of the report is available for free from The Constitution Project.