The Department of Special Investigation (DSI) expects to wrap up its probe into the murder of Karen activist Porlajee "Billy" Rakchongcharoen and file charges by the deadline.
"We still have time, so we will continue to collect evidence and make the case watertight. We don't want to leave any loopholes," DSI director-general Pol Col Paisit Wongmuang told the media on Wednesday.
Suspects for the murder were arrested on Monday, after which the DSI has two months to submit the case to court.
Pol Col Paisit spoke after key suspect Chaiwat Limlikit-aksorn, former chief of Kaeng Krachan National Park, claimed there was a loophole in the case.
Speaking to Channel 3 on Wednesday, Mr Chaiwat insisted he was innocent and claimed DNA evidence may have been fabricated against him.
He said an unnamed influential figure had framed him, in retaliation for his past crackdowns against land encroachment.
Mr Chaiwat and three other suspects -- Bunthaen Butsarakham, Thanaset Chaemthet and Kritsanaphong Chitthet -- were granted bail after they answered charges in the murder case on Tuesday.
In addition to premeditated murder, Mr Chaiwat, Mr Bunthaen and Mr Thanaset are accused of detaining, robbing and threatening the victim with weapons, and concealing his body. Mr Kritsanaphong is accused of helping them.
Porlajee went missing in April 17, 2014 while he was helping relatives to sue Mr Chaiwat for setting fire to their villages during forest evictions in Kaeng Krachan National Park. Mr Chaiwat and park officials were earlier charged over his disappearance but were acquitted due to lack of evidence.
The DSI reopened the case in June and launched a murder probe after finding skull fragments in Kaeng Krachan reservoir that matched the DNA of Porlajee's mother.
