Do I need a Lawyer to attend a meeting with SSDI Administrative Law Judge?

I assume you actually mean your hearing for disability before the ALJ.  You are not required to have a representative. However if you represent yourself you are expected to know the sequential evaluation process for proving your claim, what type of evidence and burden is required for each of the five steps, what objections to raise to evidence and testimony and to properly cross examine the medical experts and or vocational experts that may be at your hearing.  You must alos know how to present the expected hypotheticals at step 5. Also you must be expected to know how to preserve the record should your case be denied and you must make an appeal.