Requirements
Before going on a jungle trek, some things have to be taken care of.
A few items you need to bring:  
* Extra pants and shirt with long sleeves for during the night 
* Closed shoes, long trousers and T-shirt for the actual trekking. Flip flops or sandals for the camp site. Keep in mind that shoes will become wet and dirty in the rainy season (approx June to October).
* Hat or cap 
* Sunlotion, insect repellent
* Lightweight coat or fleece (October /March)
* Small towel, toiletry, bathing suite
* Lighter

* Flash light

* Personal basic first aid kit

The total weight of a back pack set is 5.5 kg (excluding personal items)

Do's and Don'ts
When you go on a trek you always wear boots or shoes, which protect your feet, long pants. A hat or cap you might want to consider. Apply insect repellent from the ankle to just under the knee to avoid leeches in the wet season.  

Etiquette
When we visit an indigenous family, we always wait until the ranger has permission to enter the house. We never enter a house without explicit permission of the owner.  All indigenous people are animists. For them the spiritual world has high respect but also fears. Some of them believe that their souls are caught in your camera when you take a picture. Others they don't want to be photographed. Always ask permission if you want to take a 'close up'. We never pay money in return for a picture.

Gifts
If you consider to take some gifst for the local cummunities baloons do a great job as well as pencils and notebooks. Please don't give money or candy.

Indigenous people

There are over a dozen indigenous ethnic groups living in the highlands of Cambodia. These groups are often referred to as highlanders or hill-tribes, due to the fact that their traditional terrain has always been the upland forested regions where they cultivate hill rice. The northeastern region of the country is inhabited by the most diverse indigenous population, being home to the Brao, Jorai, Kachac, Kraol, Kraveth, Kreung, Kuy, Lun, Phnong, Stieng and Tampuan groups.

In general terms the highlanders can be distinguished from their lowland neighbours not only by their long-standing inhabitation of the upland areas but also by their distinctive religion, which is bound to their surrounding environment, and by their use of semi-nomadic swidden agriculture techniques. According to local belief systems, the entire natural environment--the sky, earth, forest, water sources, hills, stones and rice fields-- are populated by a vast array of spiritual forces. These religious beliefs inspire both respect and fear, as the spirits are believed to have the power to influence the health, well-being and prosperity of villagers. For example, the primary forest areas surrounding villages are believed to be inhabited by forest spirits and it is forbidden to cut down trees in these areas. Doing so would arouse the anger of the spirits, resulting in the sickness or even death of the individuals responsible. In addition to these spirits of the natural world, spirits of the ancestors are also believed to have the power to protect or, if angered or not propitiated effectively, wreak havoc on the human world. At crucial stages of the agricultural cycle, in cases of illness where supernatural interference is believed to be the cause, in times of severe misfortune, or on other significant occasions (such as weddings or funerals), these various spiritual forces are offered animal sacrifices and rice wine as part of an organised communal ritual. 

Village structures vary from group to group. Kreung villages are constructed in a distinctive circular fashion with larger houses occupied by the heads of each extended family group built facing inwards towards a central longhouse where village meetings, communal feasts and ceremonies are held. All of the houses in the village are constructed from forest materials, wood and bamboo, and built on stilts, with leaf or bamboo tile roofs. Smaller houses form an inner circle and are built in the vicinity of and often facing the larger houses. These smaller houses are inhabited by unmarried teenagers or individual nuclear families of couples and their children, all of whom are still under the authority of the elders of their family group.

and burn: swidden cultivation In traditional upland rice cultivation, forest areas are cleared by family groups and burnt to establish plots of land which are farmed for several years and provide families with their food staple of hill rice, together with fruits and vegetables. The pace of village life is governed by the agricultural cycle. The traditional system of upland rice cultivation is part of a long-term cycle in which new plots of land are cleared every year, allowing previously farmed plots to lie fallow until the forest cover grows again, by which time the land regains its fertility and is fit to be reused. Before clearing new areas of land for hill rice cultivation, spiritual approval must be procured. The head of the family group that wishes to cultivate a new area must first visit the site and make a few cuts to the trees there. Their dream the night after this visit is interpreted as a sign as to whether or not it is acceptable for the plot to be farmed. A dream o
catching many fish, for instance, is seen as a good omen; a dream of fire is bad. Signs in the forest around the proposed field are also taken into account--if a snake is seen or the cries of a deer are heard, then the plot will not be cleared. Such signs inform much of villagers' time in the forest. It
may be worth clarifying at this point a few stereotypes about the nature of the swidden agriculture (or "slash and burn" as it is sometimes termed) practised by the highlanders. One widely held notion is that this method, by its very nature, is damaging to the environment. Prevailing contemporary
theories, however, appear to be that this technique is perfectly sustainable and is, in fact, environmentally sensitive as long as population pressure on resources is limited, in other words, there is no drastic reduction in the land available or a sudden increase in the population utilising a given area.

Source: The Indigenous Highlanders of the Northeast: An Uncertain Future Joanna White