Twitter has been “on top of” product and monetization improvements, and the stock market is starting to take notice, Steve Ballmer told CNBC on Friday.

“Twitter is a very good asset,” said Ballmer, a major investor in the social media company.

“So improving the products some and improving and making the monetization better, I think the company has been on top of both of those things,” the billionaire former Microsoft CEO said in a “Squawk Box” interview. “The market understands that. And it is now getting somewhat reflected in the stock price.”

After a swoon starting in mid-May, Twitter shares have soared nearly 16 percent since June 16, based on Thursday’s close. So far this year, Twitter is up 18.5 percent.

But since its November 2013 initial public offering, Twitter stock has dropped more than 50 percent.

Twitter can’t take its foot off the gas, Ballmer said. “They still have their work cut out for them. And their path could be way up, relatively sort of gently up or something else.”

Ballmer, also the owner of the NBA’s Los Angeles Clippers, described his investments. “I am an investor in Microsoft, index funds, Twitter, and then a few private things that fit in the context of sports.”