Thitisan Utthanaphon also denied media reports that he was suffering from bipolar disorder, according to his lawyer.
Chokechai Angkaew, who is representing the accused, said he met his client at Phitsanulok prison last week and Thitisan was mentally stable.
Mr Chokechai said the suspect and his legal team will fight the case on the grounds that although an assault was committed, there was no intention of killing the victim.
Thitisan has been charged with premeditated murder by means of torture, unlawful deprivation of liberty and malfeasance.
The former Muang Nakhon Sawan police chief could get the death penalty if found guilty.
Assault leading to death without intention, or manslaughter, however, carries a 3–15-year jail sentence, said a police source.
Mr Chokechai said Thitisan insisted that although he covered the victim’s head with plastic bags, he had no intention of killing him.
“Investigators have the right to press a charge of premeditated murder caused by torture, but he will attempt to have that commuted to an accident as a result of physical harm," said the lawyer.
“Investigators will shine the light of truth on the case files before the court goes on to reach a final verdict,” he said.
“His bail request has yet to be made. I’ve discussed the matter with Pol Col Thitisan’s family as this case has caught the attention of the public,” said Mr Chokechai.
The former police suspect has also denied the claim that he suffers from bipolar disorder as reported by local media, said the lawyer.
It is true that officials found some “antidepressant” medicines in his room but it is normal for people under stress to use such drugs and it does not mean he is bipolar.
Earlier, some had speculated that Thitisan might try to claim diminished responsibility due to a psychological disorder.
Thitisan and the six other suspects in the fatal torture scandal were transferred from Phitsanulok to Bangkok’s Klongprem Prison yesterday (Sept 3).
The transfer request was made by the Crime Suppression Division which has taken over the case.
Pol Maj Gen Jirabhop Bhuridej, deputy commissioner of the Central Investigation Bureau, said the seven suspects had reaffirmed their denial of the accusations.