Short answer. No. The Labor Code says employment is regular where the work is usually necessary or desirable in the employer's business, and it says so expressly notwithstanding any written agreement to the contrary. A clause denying regularization cannot override the facts of what you actually do.
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
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
The article was written to defeat exactly this clause
Most of the Civil Code lets parties make their own bargain. This article does the opposite, and it says so in its first breath: the written agreement to the contrary notwithstanding, and regardless of the oral agreement of the parties. That double phrasing is not decoration. Security of tenure is not a benefit an employee can be asked to trade away as the price of being hired, so a signature on a waiver of regularization does not do what the document says it does.
What replaces the contract as the test
Once the clause is set aside, the question becomes factual: were you engaged to perform activities which are usually necessary or desirable in the usual business or trade of the employer? That is answered by what you actually did, day to day, and how it relates to what the company sells or provides. It is not answered by your job title, your pay grade, whether you were called an associate or a consultant, or which cost centre your salary came from.
Some fixed arrangements are still legitimate
This is not a rule that every worker is regular. The article carves out employment fixed for a specific project or undertaking whose completion was determined at the time of engagement, and work seasonal in nature engaged for the duration of the season. Those are real categories with real requirements — chiefly that the endpoint was genuinely identified at the start. What the article refuses to accept is a clause that simply declares you non-regular while you do ordinary, continuing work.
What matters if this becomes a dispute
Keep every contract, including the earlier ones, along with payslips, schedules, and anything describing your duties — the contract you signed is still useful evidence, just not of the thing it purports to settle. Note the dates of each engagement and any gaps, since a year of service in the same activity, continuous or broken, is a separate route to regular status. Take advice before signing a renewal or a quitclaim framed as confirming that you were never regular.