Prime Minister Abhisit Vejjajiva suffered a major embarassment after demonstrators stormed the Asean summit in Pattaya, forcing its postponement.
Asean leaders had to be evacuated from the hotel by helicopter, as Mr Abhisit declared a state of emergency in the area.
Later, he declared the protesters who took part were enemies of the state and vowed they would face legal action.
Red-shirted demonstrators from the United Front for Democracy against Dictatorship (UDD) forced their way through police and military lines to the venue at the Royal Cliff Beach Resort, disrupting the conference even before it started.
They stormed past military and police forces and broke into the hotel, prompting the evacuation of Asean leaders and officials who were staying there.
The leaders were airlifted to a military airbase nearby.
After they had left the country about six hours later, Mr Abhisit lifted the state of emergency.
"On the country's loss today, whoever declares this as victory, I will treat them as national enemies. I will do whatever I can to make sure that these people can not stay above the law," he said.
The prime minister and senior cabinet members met late yesterday to consider legal measures against UDD leaders.
A government source said security authorities planned to arrest UDD leaders, and possibly charge them with national unrest and treason.
The authorities would gather evidence that covered the leaders' speeches and activities to back the allegations that they intended to overthrow the government.
Warrants for their arrests would be sought from the court, the source said.
Funny, every time Abhisit is asked about why the PAD isn't in jail for their activities, he says the problem is out of his jurisdiction and in the hands of the court.
It seems the wheels of justice turn quickly when Abhisit is on the receiving end of tactics he used to come to power.
I don't know how Abhisit can look at himself in the mirror. This Red Frankenstein Monster is only a reflection of the politics he chose to embrace when he allied himself with the PAD and military.
Som nam na, indeed.