As suggested......opt for the suburban rail service.You might very well get a bus to Ponnamalli just outside the station but it might take you a bit longer to reach your destination.
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If you still wanna persist with a bus then look for - X88K - 60A - M88R - 88M - 188C - M88A - 88A - - - of the buses mentioned, X88K has the best frequency and please do check with the conductor or pax before boarding,i tried my best to provide the right numbers. :) and good luck,travel safely...
more... and come back in one piece :)