One of the things I love about SE Asia is how cheap and easy it is to get around. The tourist buses are generally pretty comfortable, or would be if the drivers weren't lunatics. My personal theory is that the guys behind the wheel learned how to drive on a motorbike. They graduated up to luxury buses, but they still drive like they're on motorbikes.
Swerving into oncoming traffic to passes rows of cars. Honking the horn compulsively for no apparent reason at 4 a.m. while the passengers are trying to sleep. Slamming on the accelerator then slamming on the brakes. You'll get there safely unless you look out the front window. Then you'll have a heart attack.
Tourist buses have toilets on them. About half the times these are locked. It's probably for the best because the toilets on buses look like they should adjoin the torture room in "Hostel". Pretty grim stuff.
I love the sign on the door to the toilet on a bus I took from Sihanoukville to Phnom Penh.
Translation: You can do Number One in here but you can't do Number Two. Considering the door was designed for leprechauns and you have to be a contortionist to get inside, I recommend holding it in until the bus stops.
One of the true joys of traveling is seeing signs in mangled English. Some tourists get really snarky about it. Look at this! The grammar is all wrong. Whoever wrote this is an idiot. I personally am grateful for any efforts made to make my traveling experience easier. I'd rather try to decode bad English than try to read Khmer. Usually the meaning is clear no matter how badly scrambled the translation is.
But sometimes you see a sign like this one, which I saw in the bathroom of a tourist bus.
My best guess "Please put your rubbish in the trash bin". It does provide entertainment value to what would otherwise be a fairly routine toilet break.