According to a report in the Bangkok Post:
Cambodian Prime Minister Hun Sen ordered fresh troops to the border with an ultimatum to Thailand: Pull military forces back today or the border will become a "life and death battle zone".The political situation in Bangkok is precarious, and the danger that Thai nationalist sentiment will factor into the Thai response to the Cambodian ultimatum cannot be discounted.
Hun Sen told reporters in Phnom Penh that he had warned Thailand's visiting Foreign Minister Sompong Amornvivat that without a quick pullout, Thai soldiers could face being fired upon by Cambodian troops in "large-scale armed conflict".
"If they cannot withdraw tonight, they must withdraw tomorrow," said Hun Sen.
"We have tried to be patient, but I told the Thai foreign minister today that the area is a life-and-death battle zone."
Both countries have troops that could quickly be moved into the disputed border region near the Preah Vihear temple. Background on the dispute -- which flared-up over the summer -- here.
UPDATE I: Thailand has retreated. See here.
UPDATE II: Thailand claims it did not retreat, but will not fire the first shot.
UPDATE III: Bangkok Pundit asks who's lying, and suggests Cambodia's leader is trying to take advantage of the political disarray in Thailand.