But a concerned maid who noticed he hadn't left the room the next day used a spare key to check and found him lying dead on the bathroom floor.
Police who searched the room discovered boxes of Viagra and believe that he died of a heart attack after having sex with the woman, who has not been found.
Senior officer Pitak Neonsaeng said: "There was Viagra in the room and other medicine. We're not totally sure of the cause of death yet but we think it's a heart attack.
"He had taken the girl back to his room, taken Viagra and then died. We think that after he had finished his activities he went to bathroom and died.
"Something has caused him to suddenly fall ill.
"The man had been in Pattaya on holiday. We have spoken to staff at the guest house and we he had been using prostitutes every day during his stay.
"There were no signs of assault or robbery so we're not looking for any suspects. We have sent the body away for examination. Details have been passed to the British Embassy."
Police released pictures of officers arriving at the hotel and carrying the man's body into an ambulance.
He is believed to have weighed around 15 stone, has a distinctive cat cartoon tattoo on his right calf, and been suffering with other health problems.
A maid at the guesthouse said they had seen Mr Soden drinking every day at a beer bar nearby the hotel.
She said he was seen taking the "bar gir" - a Thai term for sex worker - back to his second-storey room.
The maid, who asked not to be named, said: "It's normal for men to take girls back to their room. I saw him go back with a girl at night time but we didn't see him the next day.
"We knocked on the door but there was no reply so we went inside.
"The British man was always friendly and happy. It was a shock to see he had died. I don't think he had been dead for very long after we found him."
Pattaya - known as the 'sin city' and the 'devil's playground' - has gained a notorious reputation for muggings and deaths among tourists.
It is home to thousands of prostitutes, sex shows and massage parlours that draw in visitors from around the world.