HUA HIN, Thailand (Reuters) - Thousands of troops swarmed over the Thai seaside resort town of Hua Hin on Friday for a twice-postponed Asian leaders' summit to tackle issues from human rights and trade to climate change.

Embarrassed by protests at past summits, a security force of 18,000 and naval gunships have cordoned off Hua Hin where South East Asian leaders plan a series of meetings, first amongst themselves and later with counterparts from China, Japan, South Korea, India, Australia and New Zealand at the weekend.

Six months ago, hundreds of anti-government protesters broke through security barriers at a summit at Thailand's resort town of Pattaya, forcing some Asian leaders to flee by helicopter and abruptly ending the meeting. Protests at Bangkok's airport last year forced another summit to be abandoned.

The strong security presence appeared to keep protesters at bay, but the anti-government movement at the heart of Thailand's four-year political crisis is still overshadowing the summit.

On Wednesday, neighbor Cambodia offered fugitive former premier Thaksin Shinawatra asylum. Thaksin, ousted in a 2006 coup, heavily influences a red-shirted, anti-government protest movement from exile in Dubai. Thailand is seeking to extradite him to serve a jail term for corruption.

At least 42 agreements are expected to be signed at the Association of South East Asian Nations summit. Topping the agenda is the launch of a human rights watchdog, which critics say is a toothless body that is already discredited by having military-ruled Myanmar, seen as a serial rights abuser, as part of the mechanism.

The 42-year-old grouping is also expected to sign a declaration on climate change, discuss food and energy security, and ways to further integrate their export-oriented economies.

The fragile global economic recovery has kept protectionist issues at the foreground. Rice-exporter Thailand threatened last week to delay an ASEAN free trade pact unless it can get a "fair deal" on tariffs from the Philippines, the world's biggest buyer of the food staple.

Those differences could derail an ASEAN Trade in Goods Agreement expected to be signed this weekend, undermining a key plank of an ambitious bid by Southeast Asia and its 540 million people to build an EU-style economic community by 2015.

MYANMAR'S ELECTIONS

ASEAN foreign ministers raised pressure on Myanmar on Thursday to hold "free and fair" elections next year, and urged the junta to free pro-democracy advocate Aung San Suu Kyi.

The sentencing of Suu Kyi, a Nobel Peace Prize winner detained for 14 of the last 20 years, to a further 18 months of detention this year has prompted Western critics to dismiss next year's polls -- the first in two decades -- as a sham.

The new watchdog , called the ASEAN Intergovernmental Commission on Human Rights, has no power to punish members such as Myanmar and aims to promote rather than protect human rights.

Non-governmental rights bodies and London-based Amnesty International have expressed concerns over the body, while the U.N. High Commissioner for Human Rights says it has no clear mandate for victims of abuse.

Debbie Stothard of the ASEAN People's Forum said five of the 10 governments had also rejected nominees from civil society groups for the watchdog and have replaced them with their own. She said observers at Friday's meeting were instructed not to question the leaders.

"It's a big slap in the face for civil society. We are trying to engage with them (ASEAN)," she said. "This situation and the gag order is an irresponsible move by ASEAN governments and it will damage the credibility of the grouping."

(Editing by Jason Szep and Bill Tarrant)