CHIANG MAI, Thailand (AP) — The bucolic, once laid-back campus of one of Thailand's top universities is under a security clampdown. Not against a terrorist threat, but against Chinese tourists.

Thousands have clambered aboard student buses at Chiang Mai University, made a mess in cafeterias and sneaked into classes to attend lectures. Someone even pitched a tent by a picturesque lake. The reason: "Lost in Thailand," a 2012 slapstick comedy partly shot on campus that is China's highest-grossing homegrown movie ever.

Now visitors are restricted to entering through a single gate manned by Mandarin-speaking volunteers who direct Chinese tourists to a line of vehicles for guided tours. Individual visitors are banned, and a sign in prominent Chinese characters requesting that passports be produced is posted by the gate.

With their economy surging, mainland Chinese have become the world's most common world traveler, with more than 100 million expected to go abroad this year. In 2012, they overtook the Americans and Germans as the top international spenders, according to the United Nations World Tourism Organization.

But in Chiang Mai and elsewhere, Chinese tourists have acquired the same sort of reputation for loud, uncouth, culturally unaware behavior that inspired the term "Ugly Americans" decades ago.

Many in the tourism industry are delighted by the influx, but 80 percent of 2,200 Chiang Mai residents polled by the university in February said they were highly displeased with Chinese behavior. The survey and numerous comments on Thai social media blamed Chinese for spitting, littering, cutting into lines, flouting traffic laws and allowing their children to relieve themselves in public pools. Some restaurant owners complained of Chinese filling up doggy bags at buffets.

The low point in local-tourist relations here in Thailand's second-largest city was likely a photograph widely seen on the Internet of a person, purportedly Chinese, defecating in the city's ancient moat.

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"Unfortunately, right now, the feeling is very anti-Chinese. In order to bring out such strong feelings in Chiang Mai people, it must be really bad. Generally, Chiang Mai people are quite tolerant of foreigners," says Annette Kunigagon, Irish owner of the long-established Eagle Guesthouse.

But she and others point out that much of the inappropriate behavior applies to tour groups rather than individual travelers who are generally younger, better educated and more attuned to local customs.

Some of the censure smacks of hypocrisy. The Thais themselves are champion litterers and have notched one of the highest traffic fatality rates in the world.

Residents of Chiang Mai, a 700-year-old city rich in cultural traditions, may be particularly sensitive to some Chinese ways, priding themselves on refined, gentle manners and soft speech. Perhaps their most common complaint is how loud the visitors tend to talk. There is also anxiety, reflected in the university poll, that in tandem with the tourists an increasing number of Chinese are buying property, setting up businesses and taking jobs from locals.

Thais are far from the only people unhappy. Over the past few years, some hotels and restaurant buffets — where guests have filled doggy bags after eating — have made it clear that Chinese are not welcome. Hong Kong Airlines has trained crew members in kung fu to subdue drunken passengers and a sign in Chinese at Paris' Louvre requests that visitors not defecate or urinate on the museum grounds. Widely publicized was graffiti etched into Egypt's ancient Luxor temple reading "Ding Jinhao was here."

Chinese Vice Premier Wang Yang last year said negative conduct had "damaged the image of the Chinese people." The government issued a tourism law mainly to regulate the domestic market but which urges travelers abroad to "abide by the norms of civilized tourist behavior." It also produced a 64-page "Guidebook for Civilized Tourism" with a long list of "do nots," including nose-picking in public, stealing life jackets from airplanes and slurping down noodles.

One of the most virulent critics has been Wang Yunmei, who recently published "Pigs on the Loose: Chinese Tour Groups" after six years of travel abroad. While the book drew mostly "nasty" comments from fellow countrymen, Wang says some told her that the book should have come out years ago.

Some Chinese media commentators say improper behavior is often an extension of domestic habits. Wang says many Chinese tourists are rural people who recently acquired money through land sales but have little education and speak only their own language. If public toilets don't exist in their villages, she says, they may not know to look for them when the need arises. She also says education has also not kept pace with the rapid rise of the middle class and its growing wealth.

"It's going to take some years before they behave better. There has been a campaign in China for some time, but these things are still going on," she says.

Those who are making money off the influx are looking on the bright side.

"We have talked to many businesses and they are very happy," says Wisoot Buachoom, director of the Tourism Authority of Thailand in Chiang Mai. The gap between the city's high and low tourist seasons has been narrowed because of the Chinese influx, he says.

Wisoot says several Chiang Mai agencies are working to regulate some of the Chinese behavior, like insisting on international driving licenses for car rentals. They have also enlisted movie stars to deliver messages about proper conduct while lauding Thailand's attractions on Chinese television.

"In the past, we had some of the same problems with Westerners coming to Chiang Mai, but now we see very little of this," he says.

Even on the campus overwhelmed with Chinese tourists, Chiang Mai University Vice President Rome Chiranukrom calls it "an opportunity, not a threat, a raid." He says the experience has given his students a "reverse culture shock" that will teach them to behave appropriately in other societies.

"We live in a globalized world and need our students to see the differences with others — and these came right here for us to see," he says.

Rome notes that 60 percent of Chinese tourists to Thailand are first-time travelers abroad, coming wide-eyed and generally speaking no foreign language to a place where all signs are in Thai or English.

"We need to learn to communicate and provide information, and then I believe that many will listen, understand our culture and obey our laws and regulations," he says.

Rome himself has just started Mandarin lessons.