Short answer. Being seasonal does not stop you becoming regular. Article 280 counts a year of service whether continuous or broken, so seasons add up. A worker taken back season after season for the same activity is regular with respect to that activity, though the work itself remains seasonal.
What the law says
where the work or service to be performed is seasonal in nature and the employment is for the duration of the season
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
What the law says
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 his employment shall continue while such activity exists
Labor Code, Article 280 — Regular And Casual Employment. Read the full provision →
The words that matter are 'continuous or broken'
Employers often assume that a gap in the calendar resets everything, so that a worker who puts in four months a year never accumulates service at all. Article 280 says the opposite: 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. Broken service still counts. Three or four harvests of the same work can therefore add up to the year the article speaks of, even though you were never on the payroll for twelve straight months.
What the seasonal exception actually covers
The first paragraph excepts the case where the work or service to be performed is seasonal in nature and the employment is for the duration of the season. Note that both halves are required, and note what the exception addresses: it explains why you are not working — and not being paid — between seasons. It is not a licence to treat each season as a first day, nor a statement that a seasonal worker can never become regular. The nature of the work is seasonal; your status as an employee is a separate question.
Regular for that activity, for as long as it exists
The proviso is carefully limited. You become regular with respect to the activity in which he is employed, and the employment shall continue while such activity exists. In practice that means a claim on the same work when the season comes round again, rather than a year-round wage or a right to some different job in the enterprise. If the employer stops the activity altogether — the plantation is converted, the line is discontinued — the words the article uses recognise that the employment tied to it does not outlive it.
How to show the seasons you worked
Because the question is one of accumulated service, records are everything, and seasonal work is exactly where records are thinnest. Keep payslips, cash vouchers, time records, harvest logs, the foreman's list, and any identification card issued for each season. Photographs and messages showing when you were called in help where nothing formal was issued. Note also whether you were recalled each year as a matter of course, which is the fact that distinguishes a returning member of the workforce from someone hired afresh out of a crowd at the gate.