By 1967, the original Sir Douglas Quintet had broken up, thanks to an unfortunate pot bust in Texas; Most of the band was landlocked in Texas on probation, but Doug himself split for San Francisco; California became his home base for many years, and was the site for SDQ MK II (the group which scored their second massive hit, "Mendocino' in '68). The freakout guitar intro was undoubtedly influenced by Doug's new home in San Francisco, and the vocal is one of Doug's most upfront and raw.
As for THIS record, I'm guessing that Doug went back to Texas to record with Huey P Meaux one last time; although it's not a quintet record, Augie Meyer's unmistakable organ is present, and the two-step beat (ala "She's About A Mover") was probably also bashed out by Johnny Perez.
This song came on my ipod shuffle play, and I had all but forgotten how great it is; I had to double check my archives to make sure I didn't feature it at some point on this site. I thought I did, back in 2008 or so, but NOPE, it's making its debut here. This is a VERY scarce record, and even though it hardly ever turns up, it's usually quite inexpensive when it does.
SIR DOUGLAS - SHE DIGS MY LOVE