Actually, the Transnasional bus company intercity bus timetables can be found
here.
I agree with
jpatokal that there are no buses Singapore-Gemas. Hop on a bus in Singapore bound for Larkin Terminal in JB. For the Larkin-Gemas route, it appears there are several buses a day:
Time : 8:30am, 10:30am, 12:30pm, 3:00pm, 5:00pm, 6:30pm.
Fare (Adult) : RM 14.20
Fare (Children) : RM 7.10
Phone : +607 - 2245182, +607 - 2220045
Arrival Terminal : Gemas : G7, Bangunan MARA, Gemas N. Sembilan
Phone : +607 - 9481089