The afternoon of May 19, 2010 was a time of chaos at Zen department store after red shirts ended their protest and the Army moved into Ratchaprasong.

There was confusion, fire, a hand grenade explosion and different groups of people entering the store, Choophan Anongjanya, Central World's assistant building and area manager recalled yesterday.

Choophan testified in the Criminal Court for a case involving two red-shirt guards accused of setting fire to Central World and Zen department store. He said a group of three to five men, dressed in what appeared to be black ranger uniforms invaded the ground floor of Zen at around 3pm on May 19 last year, not long after red-shirt leaders surrendered to police and soldiers moved in, when the month-long siege in Ratchaprasong ended.

"When [the hurled object] hit the floor, we saw it was a hand grenade and ducked for cover, and then it exploded," he told the two presiding judges. Nine of Choophan's men were injured, with eight taken to hospital.

Choophan told the court he earlier encountered at least three more groups of people: looters stealing and vandalising shops, and smashing windows; three to four hooded men who threw cooking gas tanks into the ground floor of Zen; and 40 to 50 men armed with slingshots shooting at them. They seemed to be unconnected and came from different directions, he said.

Asked later by The Nation if he knew who the people behind the arson were, Choophan said he didn't really know. "Nobody really knows," he said.

The cost of damage incurred by the fire that engulfed Zen department store was also fiercely argued with another witness. Teeraphong Methaphan, 41, director for construction at Central said in the morning Bt700 million of damage was done to Zen department store and tower.

But defence lawyers for Saichon Paebua, 29, and Pinij Jannarong, 27, who face a possible death penalty for alleged arson and causing death due to arson, argued that it was not right for store staff to come up with damage figures without an independent survey.

The defence lawyers will cross-examine Choophan next Tuesday. They told The Nation it would be a grilling.

Shackled defendant Saichon, who has not been granted bail since his arrest a year ago, was seen reading the palm of his fellow defendant, Pinij, who shared a handcuff, and was also shackled, while listening to the trial. Saichon later told a female supporter he owes money to the Corrections Department as he has ordered special food because he can't bear the food given to inmates.

"I want to go home," said Saichon, who is often described by those who knew him as not mentally sound.

The first two witnesses produced by the prosecutors yesterday said they had never seen or met the two defendants before, while the third witness, Choophan, has yet to be asked that question.