Short answer. Two consequences stack. Article 41 provides that a non-resident alien who takes up employment in violation of this Title and its implementing rules is punished under the Labor Code's penal provisions, and that the alien worker shall in addition be subject to deportation after service of his sentence.
What the law says
Any non-resident alien who shall take up employment in violation of the provision of this Title and its implementing rules and regulations
Labor Code, Article 41 — Alien Cannot Change Employer. Read the full provision →
What the law says
In addition, the alien worker shall be subject to deportation after service of his sentence.
Labor Code, Article 41 — Alien Cannot Change Employer. Read the full provision →
The order the consequences come in
The article's closing words are precise about sequence: In addition, the alien worker shall be subject to deportation after service of his sentence. Removal is not an alternative to the criminal consequence and it does not come first. The provision contemplates the penal side running its course, with deportation following it. People often assume the worst case is being put on a plane, and plan around that. The text describes something heavier and slower, which is why this is not a matter to leave until an inspection or a complaint forces it.
What counts as the violation
The trigger is Any non-resident alien who shall take up employment in violation of the provision of this Title and its implementing rules and regulations. Note that it is not confined to having no permit at all. Working outside what a permit covers is also employment taken up in violation of the Title — the foreigner who moved to a different employer, or into a different job, without the prior approval the same article requires. A valid-looking permit in a drawer is not the answer to this question; what it authorises is.
What the article does not tell you
Article 41 does not itself set out the penalty. It points to the Labor Code's general penal provisions, which is where the punishment for offences of this kind is fixed, and it is those provisions rather than this article that determine what a court may impose. Anyone quoting you a specific fine or term on the strength of this article alone is going beyond what it says. The article settles that there is a penalty and that deportation follows it; the measure of the penalty is found elsewhere.
If this is already happening
The facts that matter are documentary and can be assembled quickly: whether a permit was ever issued, in whose favour, for which employer and which post, when it was issued, and what work has actually been performed since. Gather the permit, the contract, payslips and any correspondence about a transfer or change of role. Because the consequences here fall on the worker personally and reach his ability to remain in the country, this is worth putting in front of a lawyer at the first sign of an enquiry rather than after one.