What should I include in my Employment Confirmation Letter for a DTV application as a remote worker?

Hello all, I would like to get some feedback from you all on something as I will soon be trying to apply for the DTV.

Regarding the "Employment contract or employment certificate" that the application asks for: I am a remote worker, employed by a company based in the U.S. That is to say, I am an employee of that company. But I don't have a contract with them. I believe they call it "at-will" when you don't have a contract, which mean either party may terminate the employment at anytime. In this case, is it okay just to have my employer write a letter addressed to the embassy stating my name, what I do, etc, and that they give me permission to work remotely in Thailand? I found a template online that someone else used, they call it a "Employment Confirmation Letter". Will this be sufficient in place of a contract?

Secondly, I understand that a salary amount needs to be listed in this letter. Do you know if it should be monthly or yearly? In my case, I'm still considered an hourly employee where I clock in and clock out when performing work duties. And so my paychecks are not always the same amount, as it depends on the number of hours. I'm wondering if I can just use the yearly amount reported on my 2024 W-2 that I used when filing my tax return.

Thirdly, some of the examples I seen others use for this employment letter, it was signed by the owner. Do you know if the letter specifically needs to be signed by the owner or can the General Manager's signature also be sufficient.? In my case, the owner hardly ever visits the property. It's the General Manager that I report to and oversees all of my work. And it was the General Manager that I originally went to asking about working remotely. The owner of the company basically leaves all of the decision making up to the General Manager. But I'm not sure which is the more appropriate signature in this case, or if either will do.

And lastly, are there any other additional documents my employer needs to provide other than this permission letter? Of course I will provide payslips too (I assume 6 months worth?), but I have access to my payslips myself. Just wondering if there's any other information that the company I work for needs to provide?

Thank you in advance for your help.