Showing The Way We Die Now by Charles Willeford

Sergeant Hoke Moseley is struggling: his division chief is making ominous plans for him, a man he sent to jail for murder has moved in across the street, and he's stuck on one of his toughest cold cases yet. So the last thing he needs is to be sent undercover just as he's beginning to make some headway with his work.
South of Miami he is taken as a migrant worker to a farm where rumours of murder and slavery are rife. With only a Filipino prostitute and his own wits to protect him, Hoke faces vicious rednecks and his own scheming boss in this funny, vibrant masterpiece of hard-boiled fiction, the final Hoke Moseley.