Originally recorded by Wayne Carson Thompson (1969).
Hit version by The Box Tops (US #18/UK #22/CAN #9/AUS #7 1969).
Also recorded by Gin Blossoms (1994).
From the wiki: “Wayne Carson Thompson performed professionally as ‘Wayne Carson’, and was a Nashville-based musician, producer and songwriter. Among his songwriting credits were ‘The Letter’ (also recorded by The Box Tops), ‘Always On My Mind‘, and ‘She’s Actin’ Single (I’m Drinkin’ Double)’.”
The Box Tops, “Soul Deep” (1969):
http://youtu.be/–f55NUHGbo
Gin Blossoms, “Soul Deep” (1994):
http://youtu.be/-SAFTx3HXhw