SFV Origins of some things

 Bison based on Yasunori Katō, from Teito Monogatari. Yep, checks out. https://www.sideshow.com/blog/street-fighter-15-things-you-never-knew-about-m-bison/

Quote: "M. Bison is based upon Yasunori Katō, the protagonist of a famous series of novels, which are referred to as Teito Monogatari. The series would go on to sell millions of copies in Japan and spawn numerous adaptations. Katō is believed to be a demon given human form, who has been trying to destroy Japan through numerous supernatural schemes for centuries. His most iconic outfit is a military uniform that he wore when he joined the Imperial Japanese Army. 

Yasunori Katō is considered to be an important figure in Japanese literature. He also inspired the designs for General Washizaki from Riki-Oh and Shiliew of the Rain from One Piece."

And quote from poster TheEnd, https://www.resetera.com/threads/street-fighter-a-beloved-franchise-drenched-in-racism-cashing-on-racial-stereotypes-for-30-years.18543/page-16:

Bison's design is originally based on the villains Yasunori Kato from the anime OVA series Doomed Megalopolis (who was just some hellbent dark occultist wizard taking up fashion based off some of the WWII Japanese army) and Washizaki from Riki-Oh manga, but I'm sure they channeled certain aspects of Bison's character from parts of Nazi Germany, most possibly.

But, based on what's very likely his original inspiration for a design template I don't think Bison was ever intended as a literal stand-in for Nazis or is even Thai tbh (bios say he's Japanese, which makes sense).

BTW here are the characters I'm referring to:

Riki-Oh Washizaki:

Doomed Megalopolis Yasunori Kato:

Also according to https://www.sideshow.com/blog/street-fighter-15-things-you-never-knew-about-m-bison/  , "Vega was originally meant to be an updated version of Geki, a claw-wielding ninja from the original Street Fighter". 

But Bison must be Thai, back to that resetera.com thread:

What is this you say, he loses the star to gain the Shadaloo symbol, eyes change a bit, and he's no longer Asian (cheekbones change, nose change)... ah ha::

Twitter person Patti Black @pattiblacxk says: "That's cool, I'm kinda wondering how much of the cast is lifted/homage now lol. Like I know guile is Stroheim (also Rose in Alpha is Lisa Lisa), and Balrog is Tyson. Could make for a fun little chart". https://twitter.com/Protoman/status/1158833426876784648

Perry the Canon Nihilist @sillyrookie_art Aug 7, 2019: "Guile and Rose are literally Stroheim and Lisa Lisa from Jojo part 2. They did this alot."

Lisa Lisa, and then came Rose. But seems to be Dr. Who's Tom Baker version had the long scarf first, ah ha!: