TNSRTC busses are available from the opposite of the railway station. Plz try to get a nice bus for the trip as TNSRTC busses are so badly maintained. the problem with such busses is that the busses stop only at Very important stops in kerala and stops at each and every stop in TN.
If u get KSRTC busses, the busses are much more spacious, neat and stops at IMportant stops both in Kerala and TN.
Now to Identify kerala and TN busses,
Kerala...
more... busses will be painted red and yellow while the TN busses will be having White colour busses.