What should I do if my Non-B Visa stamp indicates a shorter stay than expected?

A user with a Non-B Visa discovered that their entry stamp initially thought to be valid for 90 days is only valid until March 26 instead of May 26. They are seeking advice on how to resolve this issue in Chonburi. Commenters suggest visiting the immigration office to get the stamp corrected, emphasizing the need to arrive early due to potential crowds.