The 39 people, customers and staff, caught at a Nakhon Ratchasima restaurant serving alcohol and opening after hours on Wednesday night have each been fined 12,500 baht.
They were also given suspended two-month prison sentences.
The 28 diners and 11 employees were arrested at the Lamer Restaurant & Karaoke.
The restaurant was raided about 10.30pm on Wednesday by police and local officials. It was operating outside legal hours, there was live music and people were being served alcohol - all in breach of the emergency decree.
Mr Narongchon said provincial authorities would also take action against the operator of the restaurant.
Businesses must strictly abide by the law during the Covid-19 outbreak, police said. They advised people and businesses to be more patient with the restrictions, as the situation would soon improve.
