UPDATE 3-Cambodia PM says Thai border row getting worse

(Adds Thai PM, updates protest)

By Nopporn Wong-Anan

KANTARALAK, Thailand, July 17 (Reuters) - Cambodian Prime Minister Hun Sen said on Thursday a border row with Thailand was "worsening" and urged the immediate withdrawal of Thai troops from a disputed ancient temple.

In a letter to Thai Prime Minister Samak Sundaravej, Hun Sen said the stand-off at the Preah Vihear temple was "very bad" for relations, but he still hoped to "resolve the problem through negotiations" at a border meeting on Monday.

"The situation is worsening due to a continuing increase in the numbers of Thai military" and the presence of Thai protesters, said Hun Sen, a former Khmer Rouge commander who faces a general election next week.

With hundreds of Thai and Cambodian troops facing off on the border, there are fears it could escalate five years after a dispute over another Cambodian temple, Angkor Wat, saw a nationalist mob torch the Thai embassy in Phnom Penh.

Cambodia's listing of the temple as a World Heritage site triggered a political uproar in Thailand stoked by groups seeking to oust Prime Minister Samak Sundaravej's shaky ruling coalition.

About 2,000 Thai nationalists were stopped from rallying at the temple on Thursday, some clashing with Thai villagers angry at the loss of cross-border trade. Some protesters suffered minor injuries before riot police intervened.

"Go home, go home, you troublemakers!," one woman shouted at members of the People's Alliance for Democracy (PAD), which is leading a nearly 2-month old street campaign against Samak, whom they accuse of being a proxy for former prime minister Thaksin Shinawatra, who was ousted in a 2006 coup.

In Bangkok, Samak said the protesters were "insane" and he accused them of trying to provoke a border confrontation.

LONG-RUNNING DISPUTE

The 900-year-old temple has been a source of tension for decades since the International Court of Justice ruled in 1962 that it belonged to Cambodia, a ruling that still rankles Thais.

The latest flare-up was sparked by Bangkok's support for the UNESCO listing, which the PAD said was tantamount to selling out Thailand's heritage.

Foreign Minister Noppadon Pattama quit last week after a Thai court ruled the joint communique he signed backing Preah Vihear's listing was illegal because it was an international treaty that required parliament's approval.

The PAD seized on the court ruling, vowing to go after the rest of Samak's cabinet and step up a street campaign that has worried investors. The main stock index has dropped 23 percent since the protests began on May 25.

"Political temperatures will rise inexorably, and Thailand will become increasingly ungovernable, in the interim," Chulalongkorn University professor Thitinan Pongsudhirak wrote.

Thailand and Cambodia have deployed hundreds of troops since Tuesday when three Thai activists were briefly detained on the Cambodian side for trying to plant a Thai flag there.

Despite the aggressive rhetoric from both sides, the situation at the temple has remained calm while diplomatic efforts get underway.

Defence ministers from the two countries will attend a border meeting on Monday "so that both sides can discuss issues together in a spirit of neighbourliness", the Thai Foreign Ministry said. (For related story see CAMBODIA-THAILAND/TEMPLE (FACTBOX) or [ID:nBKK226744]) (Additional reporting by Ek Madra in PHNOM PENH) (Writing by Darren Schuettler; Editing by David Fogarty)