The Songkhla Provincial Court will give its verdict in November over the alleged use of excessive force by police to disperse protesters during an anti-pipeline demonstration in 2002.
The protesters from Songkhla's Chana district were dispersed in Hat Yai as they tried to submit a letter to the prime minister.
Rassada Manurassada, a lawyer for the protesters, said the interior minister at the time, Wan Muhamad Nor Matha, appeared in court on Sept 18 as the last witness for the defendants.
The court will read its verdict on Nov 27, he said.
The case was launched in 2003 by 25 protesters who were urging the government to cancel the Thai-Malaysian gas pipeline and gas separation plant in Chana.
They said the dispersion of their gathering by 38 police and government officials was unlawful, as authorities used excessive force.
Songkhla police commander at the time, Pol Maj Gen Santhan Chayanon, his deputy Pol Col Surachai Suebsuk and former Royal Thai Police commissioner Pol Gen San Sarutanon are among the defendants.
On Dec 20, 2002, the protesters gathered in front of the JB Hotel in Hat Yai to hand a letter of complaint to then prime minister Thaksin Shinawatra. While they were waiting for the premier, who was scheduled to chair a mobile cabinet meeting at the hotel, police broke up the protesters.