When is the latest I can return to Thailand on a multiple-entry O-A Visa for another year?

I have a question on timing. I received a multiple-entry, non-imm. O-A Visa from the Thai embassy in Los Angeles which states that it is valid from November 5, 2020 to November 4, 2021. I entered Thailand on December 6, 2020 and was stamped to stay until December 2, 2021. I then left Thailand on June 3, 2021 to return home to get vaccinated.

I understand that I can return and be given another year from the date I return as long as I have insurance for that period. My question is when do I need to return by to take advantage of another year? I'm guessing I just need to return by December 2, 2021 but I wanted to make sure. Thanks in advance.