Yes, it would be a theft, and the rub lies in the statement "never bring it back".
The question is: why would it be a theft? Simply because a company is a different entity separate from its shareholders, even if the shareholder owns a majority of the shares. Under most modern countries' corporate laws, there is a distinction between a "natural" person and a "legal" person. A "natural" person is a human being, while a "legal" person is a legal entity. Thus, both are completely separate, and taking the property from one to the other is theft.
This is because the "legal" entity is owned by its shareholders who, under the agency principle, appointed a board of directors (or simply directors when there is no board in some countries) to run the company on their behalf with the goals usually set in modern countries' laws to "maximise shareholders' value".
Taking this laptop and "never bring it back" is not within the scope of duty of the CEO nor does it serve the purpose of maximisation of shareholders' value nor the operational mandate received by the shareholders.
The CEO could be compensated in kind by a resolution of the supervising board and thus receive the laptop, and since it would be approved, it would not be theft.
Another way would be an allowance to use the laptop at home, presumably for work-related activities, as long as the CEO is an employee of the company.