  Considering the importance of investigating the transit timing variations
(TTVs) of transiting exoplanets, we present a follow-up study of HAT-P-12b. We
include six new light curves observed between 2011 and 2015 from three
different observatories, in association with 25 light curves taken from the
published literature. The sample of the data used, thus covers a time span of
about 10.2 years with a large coverage of epochs (1160) for the transiting
events of the exoplanet HAT-P-12b. The light curves are used to determine the
orbital parameters and conduct an investigation of possible transit timing
variations. The new linear ephemeris shows a large value of reduced chi-square
= 7.93, and the sinusoidal fitting using the prominent frequency coming from a
periodogram shows a reduced chi-square around 4. Based on these values and the
corresponding O-C diagrams, we suspect the presence of a possible
non-sinusoidal TTV in this planetary system. Finally, we find that a scenario
with an additional non-transiting exoplanet could explain this TTV with an even
smaller reduced chi-square value of around 2.
