No tourists were on board, Phuket Tourist Police confirmed.
The incident occurred at about 10:50am at Coco Pier in Ao Makham, where flames engulfed the vessel and triggered an emergency response.
Authorities were able to bring the fire under control and prevent it from spreading to nearby boats.
Five people ‒ two women and three men ‒ all of them were crew members on the boat, sustained burn injuries and were transported to hospital by Kusoldharm Phuket Foundation rescuers.
Initial reports also indicated that one male tour guide is missing and is believed to have been on the boat when the fire broke out. A search operation is currently underway.
The cause of the fire has not yet been confirmed and remains under investigation.
Multiple agencies responded to the scene, including the Phuket Provincial Disaster Prevention and Mitigation Office (DDPM), Wichit Municipality, the Phuket Provincial Administrative Organisation (PPAO) and other relevant units, supported by fireboats.
Officials have cordoned off the area and urged the public to avoid the vicinity to allow emergency operations to continue.