Kuala Lumpur International Airport: Bahau has no airport. The sensible arrival is a pre-booked car or Grab/direct taxi from KLIA: roughly 2–2½ hours in normal traffic and about RM180–280, with tolls worth confirming upfront. Do not try to build an airport-bus itinerary around Bahau; there is no simple, useful direct public-transport transfer.
Bahau railway station: Bahau is on KTMB’s East Coast Line, better known as the Jungle Railway. The station is close to town—about 5–10 minutes by car—but train frequencies are limited, so book around the timetable rather than treating rail as hop-on transport. From Gemas, where the East Coast Line meets the west-coast trunk route, expect roughly an hour onward by train when connections work; fares are generally inexpensive, but schedules matter far more than price.
Gemas railway station: Gemas is the practical rail junction for travelers coming from the Kuala Lumpur/Singapore corridor. Change there for a KTMB East Coast Line service toward Bahau; there is no direct Kuala Lumpur–Bahau train according to the current Jungle Railway guidance. If the connection is poor, a road transfer from Gemas is about an hour, but arrange it in advance—this is not a station with a dependable taxi rank for spontaneous long rides.