I used to live in the US but I moved back to my country last year. I was wondering if it's possible to have my relative who is a US citizen submit tax returns for me?

I worked in the US for almost 3 years and moved back to Thailand last year. I'm preparing my tax returns now and would like to know if I can have my relative who lives in the US submit the returns for me. If that is possible, would we need a letter or something to show I give my consent? Thanks in advance.