But one hospital stands out from the rest.

The Sihanouk Hospital Centre for Hope in the capital Phnom Penh is funded by foreign donations, staffed by a mixture of local and international medics and, unlike other Cambodian hospitals, it offers free treatment.

But the centre has become a victim of its own success, with demand now far outstripping capacity.

So the patients themselves have come up with a novel system to decide who gets an appointment with the doctor - a daily lottery.

At just seven o'clock in the morning, a crowd had already gathered in the car park of the Sihanouk Hospital.

Some people had been waiting all night, their cooking pots and mats piled up under a shelter near the gate.

Charb Sorn, a woman with closely cropped grey hair and a pained expression, was one of them. She looked a lot older than her 48 years.

"I travelled 40km (25 miles) from my village because I heard you could get free treatment here. I don't have money to pay at other hospitals. I have had problems with my chest for a while now. I have a lot of children waiting for me at home, so I hope I get to see a doctor quickly," she said.

If Charb's condition had been life-threatening, she would have been seen by a doctor immediately.

But after an initial assessment from the medics, she was told to rejoin the crowd waiting outside one particular wing of the hospital.

Large crowds

The Centre for Hope aims to provides high quality, free treatment to anyone who needs it. Dr Gary Jaques, executive director of the centre, said word had spread.

"Sixty percent of our patients now come from the provinces, provinces that are one or two days difficult drive over bumpy roads," he said.

"Patients have heard about the hospital and they make their way here, often in desperate circumstances. So it does create a demand that exceeds our capacity to deliver and supply. It has caused what you see here today - the crowds."

So who decides which patients will get the treatment they need? Lady luck, apparently. It was the patients themselves who came up with the solution.

Those waiting outside in the hospital grounds form themselves into a big circle, and a hospital official goes round the circle stamping today's date onto their hands and then writing a number next to it. The numbers are copied onto pieces of paper and put into a big cardboard box.

Then the real drama begins.

A hospital official stands in the centre of the circle, picks up the box and begins to shake it in front of the expectant crowd - on the day we visited it was several hundred strong.

Then, one by one, with pantomime-like choruses of "ooos" and "ahhs", the numbers are drawn.

It may seem arbitrary, but Dr Jaques said the lottery system was both open and fair.

"We don't ask anything about their income, where they're from, sex, age, race, religion. All those factors are removed. There's no opportunity for bias because the lottery is very impartial in that respect," he said.

Winners and losers

The Centre for Hope has plans to link up with other state hospitals to provide training and assistance so that standards elsewhere might be improved.

In the long run, that should reduce the pressure, but for now the lottery is many people's best hope of affordable health care.

"This was the first time I tried and I was lucky," said one of the day's 10 winners we met - 43-year-old Yane.

"I'm so excited and happy. I was so busy at home, I only came here when my condition got much worse," she said, clutching a baby to her breast.

Now in the system, Yane will be looked after for as long as she needed treatment.

But others were not so fortunate. Charb Sorn's number did not come up. She sat on her haunches, her head in her hands.

"I've lost hope." she told me. "I'll have to try again. But I only have enough money to stay here for maybe three more days, then that's it."

As the other unlucky losers drifted away, Charb collected her rattan mat and prepared to wait for her next chance to enter the medical lottery.

Maybe tomorrow her luck will change.