"We don't know what happened, we don't know anything about Thai politics," said one German tourist. "They keep telling us we are on standby, but they are still not sure if our flight can take off."

He was among 15,000 passengers stranded in Phuket since anti-government protesters marched Friday on the island's airport, the nation's second-busiest, forcing a cancellation of all the nearly 120 daily flights.

Similar protests temporarily closed down the airport in nearby Krabi and the southern commercial center of Hat Yai, cutting off air traffic to much of southern Thailand.

By Sunday, all three aviation hubs had resumed services, but protesters have threatened to return to airports, including Phuket, the crown jewel of Thai tourism - an industry that generates 6 percent of the economy.

The anti-government protests are centered on Bangkok, where up to 25,000 people have occupied the main government complex calling for the resignation of Prime Minister Samak Sundaravej.

The protests turned violent Friday, with skirmishes between activists and police. Only about 35 people suffered minor injuries, but Australia, Britain and the United States have warned their nationals to exercise caution traveling to Thailand, while South Korea has urged tourists to postpone their plans.

Thai tourism has weathered political protests before, when street demonstrations led to a coup against Thaksin Shinawatra in 2006.

But travelers have so far been undeterred by the political turmoil, just as they kept coming after the Indian Ocean tsunami, deadly bombings in downtown Bangkok and a fiery plane crash in Phuket.

Despite the disasters, Thailand has posted record tourist arrivals in each of the past four years. But the current protests come at a particularly bad time, with high global oil prices putting airlines under pressure and forcing many travelers to rethink their plans.

"The current political standoff will absolutely have an adverse effect on our tourism industry but the extent of the damage will depend on how long the turmoil lasts," said Prakit Chinamourphong, president of the Thai Hotel Association.

"It would be best if it ended swiftly."

Even before the protests broke out, tourism growth showed signs of slowing. The Tourism Authority of Thailand expects 15.48 million arrivals this year, up slightly from 14.46 million last year.

The government agency has revised down its forecast for next year, predicting 16 million people will visit Thailand, generating 600 billion baht (HK$136.9 billion) in revenue.

The slowdown has been largely blamed on soaring oil prices, which have taken a heavy toll on flag carrier Thai Airways, forcing it to cut its direct flight to New York while reducing other long-haul routes to rein in fuel costs.

The airline posted a 9.23 billion baht loss in the second quarter - its worst quarterly showing in a decade.

But some experts predict Thailand will once again rebound, in part because political turmoil there has become seen as somewhat normal.

"We're still generally bullish on Thailand," said Oliver Martin, an associate director at industry body the Pacific Asia Travel Association.

Even if the political situation deteriorated into another coup, Martin said that he did not expect many people to change their travel plans.

"If anything, the security situation with these coups is nothing new in Thailand," he said. "It's taken as fact. If you look at their history, they have coups every couple of years. Here, it's generally not violent and generally it's looked at as a domestic issue."

AGENCE FRANCE-PRESSE