Sukkot is a Jewish religious holiday, which started in ancient times. According to http://www.jewfaq.org/holiday5.htm "Historically, Sukkot commemorates the forty-year period during which the children of Israel were wandering in the desert, living in temporary shelters. Agriculturally, Sukkot is a harvest festival and is sometimes referred to as Chag Ha-Asif (in Hebrew), the Festival of Ingathering." This can be construed as having to do with giving thanks in the sense that in Jewish tradition, G-d is the source of the bounty of the land, and thus, a good harvest is a sign of G-d's favor and a reason to thank Him.

If you were referring to Thanksgiving on the other hand, that is a non-religious American holiday which many trace back to the autumn of 1621, though the actual holiday was first declared by President Lincoln in 1863. Thanksgiving celebrates the ability of the early European settlers to survive a harsh winter in the New World with the help of Native Americans. See e.g. http://wilstar.com/holidays/thankstr.htm for more details.

The only congruency is that both holidays have an agricultural connection.

Festivals like sukkot include the ritual of hallel, which means to praise. On this holiday we praise the creator for steering us through the desert life in temporary huts and for helping us to achieve fruitfulness and productivity.

We live in these huts called sukkahs: http://www.sukkahsforsale.com and take these fruits and plants known as etrog and lulav, myrtle, willow, the four species, http://www.etroglulav.com together as part of the celebration of faith and redemption on sukkot.

Sukkot is a fall harvest festival in which Jewish people gather to feast and give thanks for the agricultural bounty.