Don't lose your head!

Your life might be in dire straits but don't lose your head -keep calm.
Obviously life wasn't woking out for one particular Russian tourist;whose head was found dangling from the Rama IX bridge over the Chao Praya river of Bangkok.
The following day the body was later found floating futher down the river.
Perhaps the ruthless killing was a warning sign to the Russia mafia to stay out of the Thai/Chinese mafia territory.
There was a note,to a mysterious woman called Cath,attached to the head.
Can CSI Bangkok solve the case;are their forensics up to it?