A work permit is the most important documentation required for those seeking employment in the country. Normally this is obtained by your company either before you arrive in Malaysia or once you arrive here. Employees and their family are allowed to enter the country on social visas issued by Malaysian Immigration officials upon arrival, however strictly speaking you should not start working until the visa is issued.
It is worth noting that the East Malaysian states of Sabah and Sarawak have their own immigration procedures and travelling from the Peninsular (West Malaysia) to East Malaysia requires separate formalities (this means taking your passport whenever you travel there). Work permits must be obtained in these respective states upon arrival.
Malaysia needs foreign workers in selected industries but not all. If you are being offered a job here it can be assumed that your employer has already determined this. If you come here seeking employment do not assume that the country requires your services. In fact many expats have come here looking for work and been disappointed. Even those offered jobs often found the promised work permit was never obtained.
The documentation for a work permit is a precise and sometimes lengthy process. Completing this by yourself is possible but may prove to be a frustrating experience - perhaps, your first encounter with "culture shock" and Government bureaucracy. There are agents who, for a fee, do the running around for such permits and for first timers, this is highly recommended. Leading companies will have this already organised so relax, let others do the hard work.
Permits will be given for varying periods from six months to several years depending on the position and the approving committee. Usually first timers get a two year visa, unless their employment contract is for a shorter period and up to five years can be given for renewal.
The permit will be placed in your passport and will note your position, employer's name and address. Dependants will also be given a permit stating that: "any form of employment is strictly prohibited". Should any dependent want to work they will have to go through a separate and personal application for a work permit.
People with employment passes will also receive an “Expatriate Identification” card called an I Kad, which can be carried around as an ID card in place of carrying a passport. It is understood that eventually dependents will receive this card. Students at international schools will also receive ID cards.
Some people choose to work without a permit and leave the country every three months (when their social visa expires), to re-enter a day or so later with a new social visa. The dangers of such a process are obvious. If done more than a couple of times, it may raise the suspicion of the Immigration Department as to whether you are merely visiting or actually working in the country.
Apart for being illegal, the odds of being found out and the possibility of being deported home is quite higher as Malaysia practices stringent laws prohibiting foreigners working in the country without proper permits, therefore this is not recommended.
For more details, check out the Immigration Department's website at wwww.imi.gov.my. There is a section in English.