How can I legally re-enter Thailand with a single entry 60-day tourist visa after traveling to another country?

Got approved / recieved my 60 day single entry tourist visa.

Realized I will be traveling out of thailand (to japan) for 4 days at the very end of my 58 day stay. I will be returning to thailand bkk on day #57. Flying back to the US out of bkk on day #58.

I understand that once I leave thailand, I forfeit the rest of my days on the 60 day tourist visa.

So how do I return legally?

Just for 24 hours before my final flight out?

(I assumed they would let me back in on a tourist visa exempt. But I called the Washington d.c. consular office and they told me that wouldn't be possible.)

Tldr: how can I reenter thailand within 60 days, on a single entry 60 day tourist visa.

Thank you.