Cambodia is HOT and VERY HUMID. It is rarely below 70 degrees, so you don't need winter clothes at all. You will be sweaty during the dry season because it is pretty hot. And you will be wet during the monsoon season. So, dry hot and wet hot.
Deodorant is different there, so bring a good supply of that with you.
Otherwise, there are LOTS of options for CHEAP clothing, shoes, and toiletries in Cambodia, so this mission is one where you can pack a little lighter and purchase things there.
Sisters: bigger cities will have feminine hygiene products, but in remote areas, pads are really the only option. Consider bringing a supply of tampons or a menstral disc or cup. Wearing makeup is pretty useless. It will just melt off or wash off, so you don't really need it.
Missionaries ride bikes.
Elders: You will need short sleeved shirts and quick-drying, light-weight, moisture-wicking pants. Pick darker colors to avoid sweat marks. Just make sure they are comfortable and durable, because you will be biking in them a lot.
Sisters: Light, flowy dresses. Dresses are cooler to wear than pants. It is best if they come to mid calf, for biking purposes. Sisters just tie them up, so they don't get in the way.
There is so much rain during monsoon season that streets are often flooded. Get comfortable shoes. Shoes most commonly worn are Keens or Jambu sandals, but sketchers sandals have also been recommended. Bring nicer dress shoes for Sundays and meetings, though. Some missionaries do wear Docs with socks, just be prepared that they will be wet. Slip on shoes are best since you remove shoes before entering homes.
Elders with shoe sizes above 12 will not be able to find shoes that fit very easily.
Bring flip flops for the shower.
Get a waterproof bag.
Get a rain jacket or poncho for monsoon season. A small, compact umbrella is also useful in sudden rain storms.
There is not really a good way to have shipped packages reach missionaries. Custom fees can be 5-10 times the cost of the package. However, there are often travelers that come to Cambodia that are willing to take packages to the mission office, though.
Bring a mosquito net and a rechargeable fan.
A filtered water bottle with extra filters is nice to have as well.
Cultural things that are worth noting:
Cambodia is a beautiful country with very humble and kind people. Rejecting any hospitality, whether food or a seat, is very offensive.
The country is mostly Buddhist, so a basic knowledge of Buddhism is helpful in understanding the people.
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