The death toll from a Thai nightclub inferno has risen to 20, health officials said, as victims continue to receive medical treatment.

The blaze broke out August 5 at Mountain B Club in Chonburi province -- roughly 150 kilometres (93 miles) southeast of Bangkok. Authorities found 13 charred bodies inside the venue.

Seven others have since died from their injuries, with the latest fatality a 50-year-old man, Chonburi provincial public health office said.

All the victims were Thai nationals.

There are 25 injured who are still receiving medical treatment in hospitals, with nine on ventilators, the local health authority said.

Flammable acoustic foam on the walls of the club accelerated the blaze and it took firefighters more than three hours to bring it under control.

A Chonburi province senior police officer confirmed Saturday that the club owners, a father and son, have been charged with causing death through recklessness and operating a pub without a licence.

"They could face more charges related to building safety and social security of employees," he told AFP.

Both have been released on bail by the local court, he said.

Prime Minister Prayut Chan-O-Cha has ordered an investigation into the tragedy.

Thailand's lax approach to health and safety regulations -- particularly in its bars and nightclubs -- has long raised concerns.

A huge fire erupted at a New Year's Eve party at Bangkok's swanky Santika club in 2009, killing 67 people and injuring more than 200.

The Santika owner was jailed for three years over the blaze, which began when fireworks were set off as a rock band called Burn played on stage.

More recently, four people died in a fire caused by an electrical fault at a club on the holiday island of Phuket in 2012.