Fast and Loose (1970)

A man wakes up in Tijuana after being left for dead with absolutely no memory. As he follows a string of clues to uncover his identity, he discovers he’s been living two different lives: one as a super-successful crime kingpin, surrounded by beautiful women, expensive toys, and a lavish lifestyle; and the other as an undercover CIA agent, but with a puny salary, no family or home life whatsoever, and zero trappings of success. There's just one problem: He can’t remember which of these two personas is his true identity.