WSJ:

The final straw for the government—as well as moderate factions in the Red Shirts—came earlier this month when the protesters and government negotiators failed to agree on a deal on what would have enabled the Red Shirts to go home in exchange for elections in November.

People involved in both government and opposition camps say Mr. Thaksin urged hard-liners to come up with fresh demands that stalled the process, ultimately leading to the talks’ collapse.

They say Red Shirt leader Veera Musikapong quit the negotiations in disgust.

“He was questioning why they were bothering to talk when Mr. Thaksin was delaying any progress,” says one person involved in the mediations. Mr. Veera is in army custody and couldn’t be reached for comment.

The Economist:

Many are asking why peace talks failed, when the red shirts had little hope of resisting the troops. Insiders say that Mr Thaksin was a serious spoiler, as were General Khattiya and other radicals. In a dysfunctional and factionalised movement, internal talks bogged down. Some leaders balked at facing criminal charges without the guarantee of bail. But the leadership was also held hostage, in part, by its own rhetoric and the emotions stirred among its followers. Many were enraged by the April 10th slaughter and unimpressed by the six-month timeline for elections. “The mob would not allow them to give in so easily,” says a senior security official.

Some red shirts complain that the prime minister’s plan was too vague and lacked teeth. They did not trust Mr Abhisit to keep his promises, and asked what would happen if he resigned or his party were dissolved for electoral irregularities (it faces a court case).

BP: From speaking to a few people in the last week, who have spoken to a number of the red shirt leaders and members of the government, the explaination by The Economist closely matches what BP has heard and that is that Thaksin was clearly opposed, but he was not the only one. The government puts all of the blame on Thaksin, but there were some red shirt leaders who wanted to push Abhisit for other firm concessions aside from the November election as they didn’t believe there would have been a November election (because of a belief that some people in the establishment who were closely aligned with the PAD were firmly against an election being held) although for at least one leader who did stay, they were keen to accept a deal by the time 40 people had been killed during the blockade and before the crackdown. By then it was too late.