26 people, including one child, died after the boat capsized in a river in central Thailand, according to Police Maj. Thanat Saengaroon.
Three people are still believed to be missing in the Chao Praya River, in the province of Ayutthaya. Those killed were Thai Muslims returning from a religious ceremony to honor a famous local cleric.
Three people responsible for piloting the boat have been summoned for investigation and face initial charges that include reckless piloting, causing other people's deaths and breaching boat registration licenses.
Under their current license, the boat drivers were allowed to carry no more than 50 passengers.
If found guilty, they will face a 10 year maximum prison sentence.
The two-deck vessel collided with a pillar on a bridge, the Bangkok Post reported.
The incident happened at around 4 p.m. (local time) as the passengers were returning to Nonthaburi, a city to the northwest of the capital, Bangkok.
The search operation was suspended when night fell Monday, but was resumed once again this morning.