Thai beauty queens who took part in a pageant last month could face criminal charges for not wearing masks, police warned Sunday, after a cluster of 22 infections emerged from the event.

Thirteen contestants and nine others associated with the Miss Grand Samut Sakhon pageant, which was held at a Bangkok venue late June, have tested positive for the virus, officers said.

Thailand is grappling with a deadly third wave of infections with 9,539 new cases announced Saturday and 86 deaths.

"There are likely to be many people involved in the pageant including contestants who violated rules and regulations," Piya Tawichai, deputy commissioner of the metropolitan police told reporters in Bangkok on Sunday.

Organisers had got permission to hold the event, but had to comply with 20 specific rules, including mask wearing, police said.

"People who attended the pageant and did not wear masks also (breached) the emergency decree and diseases control laws," Piya said.

Organisers and participants in the province-level pageant were being investigated and could face possible criminal charges, the force added.

Photos on the event's Facebook page show finalists in gowns and sashes, not wearing masks and not socially distancing.

Comment has been sought from pageant organisers.

Late last week, the Thai government announced a curfew across Bangkok and nine other hotspot provinces, which comes into effect on Monday, barring people from venturing out between 9 pm and 4 am.

Thailand has registered a total of 336,371 cases and 2,711 fatalities. Most of the infections have occurred since April.

The country is fast running out of hospital beds and the Thai government is facing heat over a slow vaccine roll-out and limited testing.