By Pasit Kongkunakornkul

BANGKOK (Reuters) - Bangkok ground to a halt on Friday after a strong earthquake shook the clogged Thai capital, causing chaos and triggering city-wide evacuations that left many thousands of people stranded for much of the day.

All urban rail systems were suspended and roads were gridlocked across one of Asia's biggest cities after the quake in neighbouring Myanmar caused tremors up to a magnitude of 7.1 in Bangkok, about 1,020 km (635 miles) from the epicentre.

The quake killed nine people in Bangkok, including eight labourers who died after the collapse of a 33-storey building that was under construction. Rescuers with dogs searched for signs of life, with more than 100 missing at the site, authorities said.

Foreign tourists, some shirtless, in bathrobes or swim shorts, had to leave their hotels and mingled with throngs of office workers evacuated from high-rise towers in Bangkok's commercial districts, many in shock at a rare quake that caused some skyscrapers to sway for minutes.

Huge crowds gathered outside plush hotels, offices and malls, and were shepherded away from tall buildings by security personnel. Many were directed towards the sprawling Lumpini Park after warnings of aftershocks, 11 of which struck the city within three and a half hours of the quake.

"I ran from the 7th floor of a mall, it was chaos. The scene was like the end of the world. People screamed and ran to find somewhere to shelter," said school teacher Yupadee Anujan, 34, who took refuge in the park.

"There were siren sounds ringing constantly .... this made me more frightened, so I tried to walk to the park as quickly as I could."

LONG MARCH HOME

Videos shared on social media showed white water pouring down the sides of the 37-floor Intercontinental Hotel as the tremors emptied its rooftop swimming pool.

Authorities in the city of more than 11 million people had received 169 calls reporting damage to buildings by late afternoon. Temporary shelters were set up around the city for people unable to access their homes.  

Buses were packed, motorcycles jostled for inches to squeeze through and sidewalks were crammed with workers trying in vain to hail taxis as traffic ground to a halt.

Vehicles on major thoroughfares were bumper-to-bumper. Many people abandoned the roads to make long journeys home on foot. 

"Just got to know the term 'disaster victim' for real today... first and last time, please," posted one social media user who took three hours to walks eight km (five miles) home.

Bangkok Governor Chadchart Sittipunt ordered four of the city's biggest parks to stay open all night and provide food, water and refuge for thousands of people unable to get home.

Among those was Natcha, who was camped out in Lumpini park late at night. She said she was scared to go back to her 10th-floor office. 

"When the quake happened and the shaking was most intense, I was not quite sure if I'd survive," said Natcha, who declined to give her full name. "The shaking was so intense."

(Additional reporting by Athit Perawongmetha, Orathai Sriring, Artorn Pookasook, Napat Wesshasartar and Juarawee Kittisilpa, Writing by Martin Petty, Editing by Timothy Heritage)