This tutorial, while somewhat humorous, is meant to help those who may travel to Asia – and to share the secrets we wish we knew before we went! This information applies only to what we have experienced in Thailand, Cambodia, and Laos, staying mostly on the well-trodden budget tourist track.
Firstly, to enter the bathroom (often called the “toilet” on signs or to ask where it is) you will almost always have to either step up or down. We think this is due to the water drainage system.
Toilet
The majority of places that visitors to Asia will go (hotels, guesthouses, tourist attractions, etc) will have Western style toilets; however, some may have Asian style toilets as well.
Western style toilets
This poem, posted in our guesthouse in Siem Reap, Cambodia, does a pretty good job explaining what you need to know:

The hose, affectionately dubbed the “butt sprayer”, is often very high powered, so approach with caution. More than you anticipated or needed (yourself and the seat) may get wet but they will air dry quickly, or you can use more toilet paper to ensure everything is dry. For some humor, you can call your travel partner into the bathroom (“I lost one of my contacts! Help me find it!”) and when (s)he enters, aim and fire with the butt sprayer! This is what we imagine our brothers would have done to us if we grew up in Asia.

Pedestal & Squat Toilets
Asian style toilets are more like a hole in the ground – like camping for most Westerners. Some are a bit off the floor (pedestal) and have grooved pads that you step onto before squatting. Others are just flush with the floor. While it takes a little bit of agility, you will want to make sure you keep your shorts/pants off the floor.

All toilets
The pipes and sewage system cannot support flushing toilet paper or anything else besides human waste, so put it in the basket next to the toilet; the basket usually has a cover. This is not a big deal as long as you use the butt sprayer (which means your TP should be clean to throw in the trash). Often times, public toilets will not have toilet paper supplied, so always carry a tissue pack with you. Some toilets will not have a built in flushing mechanism; instead, there will be a bucket of water and scoop pail nearby – simply pour a scoop into the toilet to manually flush it.

Sink
The sink will only have one knob and the water temperature will usually be room temperature. The sink water can be used for washing your hands/face/clothes but should NOT be used for drinking or brushing your teeth. Locals don’t drink the tap water either – bottled water is widely available.
Shower
This will always mystify (and frustrate) us. Most nearly all of the time, there is no tub and no shower curtain. The shower is simply a shower head (connected to an external hot water heater) mounted to the wall in the bathroom, which as you can imagine, almost always results in the whole room getting wet. Sometimes, you can even sit on the toilet and shower at the same time! Other times, the room is big enough that there is a general shower area. Just accept that the bathroom floor, which has a drain built into it, will get all wet. Outside the bathroom door will be a mat for you to wipe your feet on when going in and out. This is immensely helpful to avoid trekking water out of the bathroom to everywhere else.

Questions? Let us know!
I take it that learning how to use a toilet wasn’t one of the highlights of the trip.