Police said the incident took place at about 4.30pm on Saturday as members of an insurance company were having a party.
“Of the 18 injured, 11 were sent to Phrae Hospital, three to Phrae Christian Hospital and four to the Phrae-Ram Hospital,” Muang Phrae Police Station chief Pol Colonel Pongpeera Karaket said.
He added that at least three people had suffered bad fractures.
“The police will summon the restaurant owner for questioning,” he added.
Diner Wannee Intajuang said she and her colleagues had gathered for a celebration. “Some 50 people were attending,” she said, adding that the floor fell through when the group had gathered to take a photograph together.
She said she escaped unscathed because she was not standing where the floor collapsed.
Restaurant owner Suwit Sombat said the floor collapsed because it could not take the weight of so many people, adding that he would have warned them if he had seen them earlier.
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