Short answer. No, not under this article. Employment is deemed regular based on whether the employee performs activities usually necessary or desirable in the employer's usual business — "the provisions of written agreement to the contrary notwithstanding." A title or contract label that says otherwise does not change what the actual work establishes.
What the law says
The provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties, an employment shall be deemed to be regular where the employee has been engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
The test is what the work actually is
Article 280 defines regular employment by reference to the nature of the work itself: employment is regular "where the employee has been engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer." Nothing in that test turns on what the position is called. If the tasks being performed are usually necessary or desirable to the employer's ordinary business, the employment falls within this description regardless of the title attached to it.
Written and oral agreements do not override this
The article makes this test apply "the provisions of written agreement to the contrary notwithstanding and regardless of the oral agreement of the parties." This is a direct statement that a contract, or a verbal understanding between employer and employee, cannot redefine regular employment away from what the actual nature of the work establishes. A written agreement calling the position something else does not, by the article's own terms, change the outcome.
The two named exceptions
The article carves out two situations where this regular-employment classification does not apply: where "the employment has been fixed for a specific project or undertaking the completion or termination of which has been determined at the time of the engagement," and where the work "is seasonal in nature and the employment is for the duration of the season." Outside these two defined exceptions, work that is usually necessary or desirable to the employer's regular business falls under the regular-employment description.
The one-year rule for work outside those exceptions
The article adds a further rule for employment not covered by the preceding paragraph: "any employee who has rendered at least one year of service, whether such service is continuous or broken, shall be considered a regular employee with respect to the activity in which he is employed," and that status continues while the activity itself exists. So even employment initially treated as casual can become regular through the length and nature of the actual service rendered.