Hi Chutima,
If you have already begun receiving your old-age pensions from the OASI (pillar 1) and your occupational pension fund (pillar 2), the main implication to consider will be the impact on your tax bill. Because pensions are taxable in Switzerland, your taxable income would include both your pension income and the salary you earn from your employment. The result is that you could be pushed into a high tax bracket.
If you have not yet begun receiving your pensions, you can postpone your pillar 1 and pillar 2 pensions, and withdrawals from the pillar 3a, for as long as continue working, but at the most up to the age of 70. This will prevent receiving double income, with the possible tax implications that brings. It will also result in your getting a higher pension when you do retire.
Other than the tax aspect, the other impacts are mostly positive. You can apply to the compensation office to have the additional contributions you have to pay during your continued employment credited to your OASI pension in order to increase it (at the most up to the maximum OASI pension). You can also continue making contributions to your occupational pension fund to improve your pillar 2 pension. You also benefit from employer-based accident insurance, which is more comprehensive than the accident cover you get from mandatory Swiss health insurance.
Best regards,
Daniel