iva.croatia, you cannot have "one more job" in Qatar. There are loads of Labour and Sponsorship rules and regulations here.. before one couldn't have an extra part-time job, unless receives a written permission from the sponsor.. the chance to get one was next to zero..
but new law is even stricter.. you just cannot work for anyone other than your sponsor…the penalties are really heavy

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“You become responsible forever for what you have tamed”. Antoine de Saint-Exupéry