Two days after a police officer died in a Bangkok hotel, possibly as a result of being drugged after checking in with a male transexual, police yesterday apprehended a man at a Lop Buri hotel whom they suspect of involvement in the death.

Seksan Khamwong, 36, was located after police traced his mobile-phone signal. He was on the run driving the pickup of Pol Lt-Colonel Chanin Bunnag, who was found dead at a hotel on Suksawad Road early Wednesday morning.

The suspect admitted to drugging the officer with one sleeping pill by cracking it in his mouth and then spitting it into a can of beer for Chanin to drink. Seksan claimed he had not intented to kill the officer.

Seksan said he had known that Chanin was a policeman when they met in a pub, where, he said, the officer approached him and offered him a job as an undercover agent for drug sting operations. Seksan said he had drugged Chanin as he was desperate for money to pay tuition fees for his 13-year-old adopted daughter.

Metropolitan Police Bureau chief Lt-General Wiroj Jantharangsee dismissed Seksan's claim that he had merely committed a "crime of opportunity", as the man had once served a prison term for a similar crime and hundreds of sleeping pills were found with him.

However, no criminal charges have yet been filed against Seksan while police wait for a forensic test to determine whether the officer was drugged, or poisoned. The results should be available next week.

The initial autopsy report indicated that Seksan died of suffocation. His death could have been instigated by a stroke followed by a heart attack, according to a police coroner.

After pursuing Seksan on the basis of a recent mobile-phone signal detected in Ayutthaya province yesterday morning, police received an important tip-off from police in neighbouring Saraburi province that they had impounded a pistol thought to belong to the late officer.

Deputy Metropolitan Police Bureau chief Major Krissada Phankhongchuen said that after leaving Bangkok Seksan had met a female prison guard in Saraburi  whom he had known while in prison for a similar crime two years ago.

Quoting the unidentified wardress, the officer said she had found the handgun in a bag left with her after she and Seksan went out shopping together, and had taken it to Muang Saraburi police station and asked the officers what she should do about it. After police impounded the gun, the wardress said, she phoned Seksan to ask whether he was involved in the death of Chanin in Bangkok. Seksan denied it and turned his mobile phone off. Police are trying to discover the whereabouts of Chanin's gold necklace and other belongings.

Phet Khamwong, his mother, said she could not believe he was involved in the policeman's death. She said Seksan had had a sex-change operation when he was 22.