
The anti-government group's leaders denied that the incident had been engineered by the PAD with ulterior motives or resulted from infighting between protesters.
However, a police officer investigating the incident suggested that the bomb could have been planted by someone inside the PAD.
"It's their own bomb. It exploded inside the tent," Colonel Somchai Chueyklin was quoted by Agence France-Presse as saying, referring to a tent where the PAD's guards are stationed.
He gave few details as he was not allowed inside the protest compound at Government House.
The explosion occurred about |4am yesterday near the Santi Maitri building inside the Government House compound, where the PAD has been staging a rally for over two months.
Volunteer guard Methi Uthong, 24, was injured and sent to Vajira Hospital.
Somsak Kosaisuk, a PAD core leader, told a press conference yesterday that he bombing was "certainly the work of the government" and aimed at discouraging prospective participants in the PAD rally.
He ruled out a third party or personal dispute between fellow protesters as a possible cause. "The PAD has received threats, and there have been many attempts to interfere with our rally," he said.
Chamlong Srimuang, another PAD leader, said yesterday that security at the protest site would be further strengthened following the attack.
He also said that he did not believe the incident had been caused by a third party or a dispute between fellow PAD supporters.
Nitaya Nutrakian, 49, a participant in the protest, said the explosion had occurred not far from where she was sleeping.
"The other night a bomb exploded outside. This time it happened inside the compound. I am afraid now; I didn't think anything like this would happen. So many people are gathered here," she said.
Meanwhile Maj-General Khattiya Sawatdiphol, a specialist from the Army, yesterday repeated his warning to the PAD that there would be more such attacks if the group continued its rally inside Government House.
"The [latest] attack pointed to the high capability of the attacker. Explosions will not stop unless the PAD surrenders and leaves Government House. From now on, attacks will occur almost every night," he said.