Looks to be a 24" or 60cm frame, which would be 'too tall' for a normal 5'6" rider. I'm barely 5'8" and by most 'bike fit' calculators, I should be riding a 54 or or maybe 55cm frame - but I ride a long 57cm, My 'other' bike is a 58cm. What I am trying to say is it all depends on the 'fit' - how it fits your body size/type.

Based on a couple of the visual clues shown in your pic of the bike, it is a relatively low or entry level bike. SunTour made components ranging form basic entry level to downright outstanding quality components - it depends on which level of components you have - GT, V-GT, Honor, etc. More detailed drive-side pics would certainly help, but I'm guessing that you have a $50-75 bike there, tops.