Jobs are available throughout Cambodia, but apart from teaching English or helping out in guesthouses, bars or restaurants, most are for professionals and are arranged in advance. There is a lot of teaching work available for English-language speakers and salary is directly linked to experience. Anyone with an English-language teaching certificate can earn considerably more than those with no qualifications.
For information about work opportunities with NGOs, call into Phnom Penh's Cooperation Committee for Cambodia, which has a noticeboard for positions vacant. If you are thinking of applying for work with NGOs, you should bring copies of your education certificates and work references. However, most of the jobs available are likely to be on a voluntary basis, as most recruiting for specialised positions is done in home countries or through international organisations.
Other places to look for work include the classifieds section of the Phnom Penh Post and on noticeboards at guesthouses and restaurants in Phnom Penh.