In Biggles and the Blue Moon, Taihan was the name of the palatial private residence of the wealthy Chinese merchant Lin Seng. Located in the northeast of Malaysia near the Thai border, it was set in the shadow of the mountain of the same name and was largely surrounded by jungle. The only link to the outside world was a 20 mile private access road which led to a main road. One other detail which Johns mentions is that it is near the east coast, which is some twelve miles away.
Taihan is a fictional location. Johns states that it is named after an 8,000 ft high mountain of the same name. He was probably thinking of Gunung Tahan which, at over 7,000 ft, is the highest mountain in the Malaysian peninsula. However the location of Gunung Tahan does not eactly match that of the Taihan mountain in the novel. Gunung Tahan is located in the northeast of the Malaysia but it is not near the Thai border (some 80 miles away) nor is it near the east coast of the peninsula (also some 80 miles away).