Theft is generally a "crime involving moral turpitude". You are subject to deportation after a conviction for a crime involving moral turpitude if (1) you are convicted within 5 years of being admitted to the US (or of becoming a permanent resident), and (2) the longest possible sentence is a year or more. If the longest possible sentence is 364 days or less AND if you commit NO other crimes, you should be able to avoid deportation.
I strongly suggest meeting with an immigration attorney, however, because you have other consequences to consider in addition to just "deportability". For example, a suspended sentence of 6 months and a day could make you "inadmissible", meaning that while you may not be "deportable", you could be prevented from re-entering the country after a trip abroad.
You should also be wary of plea arrangements that avoid a conviction for state purposes - they may still count as convictions for immigration purposes. Again, I strongly suggest consulting an immigration attorney.