Kind of hard to gather evidence on the extent of the corruption of this or that officers. All Thais know/ assume that virtually all police/ governments officers are corrupt. Then ,any investigation of the graft of an individual officer would be conducted by other corrupt officials, who possibly have an agenda beyond establishing facts and evidence. It's like the Mafia with its internal code of silence, difficult to penetrate from the outside. Even worse , there is no real outside, since the whole system is rotten.
There was some hope with the MFP, a young generation fed up with politics/ corruption as usual. Tried twice, sidelined twice by the establishment.