PHUKET police are hoping that the lifeless body of murdered bar hostess Wanpen Pianchai will produce vital clues that help to snare her killer. Royal Thai Police forensic experts at the Surat Thani Identification Centre are now searching in painstaking fashion for samples of the murderer's DNA.

Colonel Wanchai Eakpornpit of Phuket City police station has posted a 50,000 baht reward for information about the mysterious blue-eyed, bearded expat - the last person seen with Khun Wanpen before her naked body was stuffed into a pull-along travel bag and dumped by a roadside in central Phuket.

He confirmed today to Phuketwan that the painstaking hunt for her killer continues on two levels: the physical search for the eye-catching expat, who is the prime suspect, and the microscopic scientific investigation of Khun Wanpen's own cadaver.

In modern murder sagas, killers are still caught by good detective work. But forensic science also has increasing importance. These days, just as many killers are trapped by sound laboratory techniques as on the run.

Khun Wanpen's naked body, stabbed twice, was found on June 24, six days after she was last seen alive, leaving the Sweethearts Bar in the west-coast resort of Kata-Karon with the blue-eyed, bearded expat who dropped by and breakfasted on a beer there.

No murder weapon has been located but a closer examination of the 34-year-old mother-of-two could reveal the size of the knife that probably killed her, along with whether she was also strangled before or after being stabbed in the chest and the back of the neck.

Did she have the chance to scratch her attacker? Close examination of her fingernails could turn up a small piece of flesh that incriminates her killer. A detailed examination of her mouth and other orifices will also be made.

The prime suspect reportedly asked at Sweethearts Bar for a katoey lady boy as a companion, but at 7am that morning, only female staff were cleaning up the bar. Did the star-crossed hostess and her customer argue about the kind of sex he wanted?

A thorough examination of Khun Wanpen's body may reveal much about the circumstances of her final moments. If the blue-eyed suspect was the killer, at some stage did he brush his beard against her naked body?

If so, the prospect exists that some of his DNA may have been left behind. Even if he has since shaved off his beard, it may have already provided an important piece of evidence.

The killer appears to have first folded Khun Wanpen's body into a black garbage bin, then into a blue travel bag. Had he used the travel bag before, and does it contain fingerprints, either on the exterior or the interior? In putting Khun Wanpen's naked body into the bag, did he leave DNA on her body, or shed some sweat, or lose a hair or two?

These are intriguing questions that form an essential part of one of the most widely-followed murder investigations that Phuket has ever witnessed.

Killings that involve expats as victims or as suspected perpetrators inevitably attract a broad degree of interest, both among Thais and the expat community. To have a murder of this savage nature in the world of sexpats ignites the concerns of all who have connections with Thailand's sordid, sex-driven underbelly industry.

Despite its seaminess and the obvious imbalance of the physical power of the women and their customers, violence is unusual and a murder is extremely rare.

While Khun Wanpen's cadaver may yet produce the evidence to convict her killer, even good DNA samples leave the police with the difficult task of apprehending the suspect.

Almost three weeks after Khun Wanpen vanished, little is known about the man who possibly murdered her. So far, the 50,000 baht reward has produced no real leads, and the sex-workers at more than 700 bars and nightlife venues across Phuket remain fearful that the killer may strike again.

A blue eyed, bearded expat who speaks a notable amount of Thai should stand out on Phuket. But nobody has come forward so far to say: ''I am positive I know this man,'' even though the colonel has provided his own mobile telephone number for information.

Is the prime suspect still on Phuket, laying low? Police believe that might well be the case. Yet one would think that somebody's suspicions must be aroused, sometime. The katoey community is especially sensitive to having mavericks in their midst, let alone a possible murderer.

An average of 6000 people leave Phuket by air every day at this time of year. Was the man one of the 120,000 people, most of them expats, who have departed the island since Khun Wanpen disappeared?

It is easy for a man with a beard to shave it off, and for a murder suspect to attempt to hide their most prominent features. Blue eyes can even be disguised with colored contact lenses.

But an alert Immigration officer, either on Phuket or in Bangkok, could be expected to compare the image in the passport with the face at the counter, and to ask questions.

Khun Wanpen herself may also yet provide some of the answers.