I went to Nepal last year with TPS Advance Parole. I have been maintaining F1 and recently I got my OPT approved. However, I noticed my i-94 doesn't have D/S and i-94 admit until date, however it has some date within 6 months after. My class of admission is also DA instead of F1. I think its because I am in TPS and but I want i-94 to be corrected without leaving the country. Anyone with same issue? Any suggestions?

You can't correct i94 when it's info is already correct. You used TPS AP, so you are admitted as a parolee not as F1 that's y u have DA in ur i94.

I can reinstate as F1 then? What options do I have and not leave the country?

Class of admission is irrelevant to your status. If your sevis is active on F1/OPT you are fine.