I hope this message finds you well. I am a licensed attorney with over a decade of employment law
experience. It is a pleasure to assist you today.
In crafting such a letter, and I will be happy to help you, you need to keep it direct, but with enough specificity that the employer fully understands you situation at the time and the reason you want to get back with the company. You need to also described your value to the company (this comes in the form of proclaiming your record without overstating things).
The template should be as follows:
RE: Request for Reinstatement
Dear Mr. Smith:
I hope this letter finds you well. I write to you to humbly request reinstatement to my last position with Company X. As you may know, I started with the company on (such and such date) and last held the position of (name the position). I served in that capacity for ___ years and feel as though I was a positive contributor at that position, as can be verified by my co-workers. During my tenure, I was able to accomplish (name an accomplishment that brought value to the company).
On (date), I submitted a letter of resignation to pursue another opportunity that I thought at the time would be better for me and my family. I have discovered this not to be the case. The grass is not always greener - it certainly was not in this case. My departure had nothing to do with your company, but with perceived opportunity. I have realized that was a mistake.
Therefore, I humbly request that I be allowed to resume my duties and responsibilities with Company A. I am available to start immediately and would be grateful for that opportunity.
If you have any other questions, or would like to speak with me in person, I am available at your convenience.
With Kindest Regards,
I have used a similar format with great success in the past in the exact same circumstance.
Let me know if you have any other questions. If not, please rate my answer positively.