What's the weather like in Cambodia in May?

It's summer all year round, so you don't need to bring thick clothes. It is rainy in August.

If you go, at least take an umbrella to keep out the sun and rain. When traveling to Angkor, you must wear comfortable shoes, take sunscreen with high SPF, prepare a pair of slippers (the hotels there don't use disposable slippers, they are beach slippers for anyone to stay in), and you can bring a bottle of mosquito repellent or wind oil.

If you don't know anything else, you can ask again. I hope the above can help you.