Doorways To Danger by Mark Napier. Sam Cape, an Australian officer is on leave from Pacific patrol duty, and picks Singapore because it’s a big place with lots to do. Plus, he’s a friend of the local police chief. After a night of hard drinking he wakes to find a nude blonde in his bathtub, strangled. How did she get there? Who killed her? Then a rich British gentleman and his daughter show up He wants him to find the murderer of his son. He’s on vacation, he tells them, but his friend in the police department was sure he would help them. It was just something that would interest him more than drinking and chasing women. This was a nice little mystery with plenty of women, Chinese Tong killers, and local crooks. My copy is the original hardback published in the UK in 1966. I can’t find out anything about the author, and I’m not sure this book was even published in the US, but it is a good story and well worth searching for.