Section 60F. (1) of the Employment Act 1955 states that an employee shall, after examination at the expense of the employer-

(a) by a registered medical practitioner duly appointed by the employer; or

(b) if no such medical practitioner is appointed or, if having regard to the nature or circumstances of the illness, the services of the medical practitioner so appointed are not obtainable within a reasonable time or distance, by any other registered medical practitioner or by a medical officer, be entitled to paid sick leave.

Therefore you can still accept medical chit from non-panel clinic on condition as stated above i.e. emergency basis having regard to the nature and circumstances of the illness. You need to query the employee on why he obtained medical chit from a non-panel clinic and only if the employer is satisfied with the answer should the employer approved the medical chit.