The inferno started about 1am as customers packed the Mountain B pub, according to Sawang Rojana Thammasathan Foundation.
Footage showed people running for safety and screaming as flames and smoke billowed from the building. Some were seen running with their bodies engulfed in flames, reported the Bangkok Post.
Nine men and four women died in the fire. Four charred bodies were found in front of the one-storey pub building, three in a men’s restroom, one at a DJ booth and five at a cashier’s booth.
Pol Col Wuttipong Somjai, Phlu Ta Luang police chief, said all victims were believed to be Thai nationals.
Mountain B covers more than three rai of land and is located on Sukhumvit Road in Sattahip.
Eyewitnesses said they heard two explosions near the DJ’s booth and saw sparks that ignited soundproofing foam, and the fire spread quickly.
Pub superviser Thanyapat Sornsuwanhiran, 26, said she saw the flamed on the roof of the pub and she and security guards tried to guide customers out through the front door.
Chon Buri police commander, Pol Maj Gen Atthasit Kitjahan, said about 40 people were injured in the blaze. Officials said eight were severely injured with burns all over their bodies.
The premises opened about a month ago and is popular with young local people. The fire erupted when customers were enjoying music, leading to a stampede for safety.
The blaze is reminiscent of the Santika pub fire in Bangkok during the New Year’s Eve countdown to Jan 1, 2009. Sixty-six people were killed and more than 200 others injured then.