Overtime pay eligibility

To keep it simple, read this as per labour law:

With regard to overtime, a worker may be employed for extra hours if this is required for in the interest of business, provided that the basic and extra hours or work shall not exceed sixty hours per week unless the Ministry of Labor and Social Affairs shall have granted permission for a long period. Payment for each extra hour equivalent to hours wages entitlement increased by a minimum of twenty five percent thereof for hours worked during the day, and by a minimum of fifty percent thereof for hours worked during the night which shall be deemed to being from seven o'clock in the evening until seven o'clock in the morning. 

When conditions of work require the worker to work on any official holidays, he shall be paid 150% of his normal wage or, he shall be granted another day in lieu thereof.

Now the tricky bit is that you cannot force your employer to comply without going to the Ministry of Labour and filing a case against him.

Thanks for answering xTang. As am getting another day in lieu thereof, I wouldn't be entitled to overtime?

Yes if you get day in lieu for working on official holidays.