The most useful short attraction in Hua Hin if you want views, a temple stop, and a better sense of the town's south-end geography.
Khao Takiab matters because it does several things at once without wasting time. It gives you the coastline view, a local religious stop, and an immediate explanation of why south Hua Hin feels different from the older center. The monkeys are part of the experience, but they should not become the whole story. What matters more is that the hill lets you understand the beach, resort strip, and wider shape of town very quickly.
Current Info: Go early or late. Midday heat makes the stop less pleasant and less useful.