You can never expunge (erase) a criminal conviction; if you did regular probation or jail time, that conviction will remain on your record for the test of your life. If you successfully completed your deferred adjudication probation, you may be eligible to seal the record from the public. If the theft was a misdemeanor, you may be able to file a motion for non-disclosure right now. If it was also a felony, you would have to wait 5 years from the discharge from the deferred adjudication probation to seal it.
Talk to a local criminal defense attorney who handles motions for non-disclosure for more information.