Police are investigating the death of a Swedish tourist believed to have been killed by a mystery woman - just two hours before an Australian was also found dead.

Mika Huotari, 38, was discovered lifeless in the bathroom floor after a woman was seen leaving his room carrying a bag at the Grand Shivalay apartment in Thai 'Sin City' Pattaya in Thailand.

Just two hours later, Michael Shane Caola, 54, from Perth, was discovered face-down in a pool of blood in the same building.

Mika was on the fifth floor and Michael was on the seventh - a 30 second walk up the emergency fire exit.

Police said they were investigating if both deaths were connected to the mystery woman, believed to be a transgender sex worker, who was seen in the apartment's CCTV footage.

Police Lieutenant Colonel Saijai Kamjulla of the Pattaya City Police Station said: 'In the case of the Swedish man found dead and naked, there were several suspicious elements.

'The bathtub had been left running until water overflowed and mixed with blood. There were also signs that blood had been cleaned up in certain areas of the bathroom, along with a wound on the victim's head.

'Police are now trying to locate a transgender woman who is believed to have been the last person with the victim, in order to question her as part of the investigation.'

The officer added that though there was no established link between the two deaths, police were not ruling out any possibilities since they both occurred in the same building within a short time frame.

Mika's corpse was discovered on July 17 at around 2:06 pm local time, after building caretaker Thanchanok Prajit, 27, knocked on his door for housekeeping.

She said she repeatedly called out to the guest inside but grew suspicious when there was no response despite the air conditioning and water running.

She said: 'When I opened the door, I was shocked to find the man lying dead in the bathroom. I fled and immediately called police. While he was staying here, he frequently brought different women to his room.'

The Swedish guest, who had been staying at the apartment since May, was found naked with a severe head wound. He was lying on the flooded bathroom floor, his blood mixing with the water that overflowed into the bedroom.

Police said they have obtained CCTV footage from the night before, which shows a short-haired woman in a black high-slit dress entering Mika's room and staying for around 20 minutes before leaving with a bag.

They added they were trying to find the identity of the 'femme fatale'.

Former fishing village Pattaya became popular with American troops on 'rest and relaxation' breaks in the 1950s and 1960s when the U.S. military had bases in Thailand while fighting Communism in Vietnam. Rural families are said to have even dressed their sons as women to cash in on the gold rush.

The handful of bars in the coastal town quickly grew and it is now the world's biggest sex holiday destination, with round-the-clock prostitution and drugs - a modern-day Sodom and Gomorrah rife with crime and debauchery.

Government chiefs have attempted to clean up the city but regular violence, depravity and claims of corruption continue to blight its reputation.