The court initially sentenced Captain Pongsak Lilapongsathorn, 34, to a life sentence and a Bt3-million fine, but lowered the punishment to 39 years and four months and a Bt2-million fine - because his testimony proved useful to the case.

As a deputy inspector at the Forensic Science Division, Pongsak's duty was to take narcotic evidence seized from nationwide drug crackdowns for laboratory testing, the lawsuit said, but he kept the drugs and then sold them.

The arrest of Kareni Sao Mo-am with one tablet of yaba at Kanchanaburi in June 2003, implicated the division's janitor Mongkol Artpaksa.

Mongkol - who was later nabbed in a police sting operation with 1,081 yaba tablets - implicated Pongsak as his dealer and that they were involved in drug trade worth Bt84,000 from 2002 to 2003.

Pongsak was arrested in another sting operation in his office toilet with 500 tablets worth Bt40,800. A search of his desk yielded another 2,194 tablets and 20 bottles of ketamine. The search was conducted in front of his supervisors.

The court considered Pongsak's claim that he was lured to the office by Mongkol who claimed his supervisors wanted to see him, and that the money retrieved from his various accounts was money he had inherited from his family, as unconvincing.