Deputy Transport Minister Atirat Ratanasate said Harbour Department officials are stepping up their investigation and questioning the captains of both boats involved, to establish the exact cause of the accident.
The captains have been charged with reckless driving causing death and injury.
Their permits have also been revoked.
To avoid such tragedies in future, the department has been ordered to overhaul boat safety measures and ensure that captains and operators meet its standards, Mr Atirat said.
A speed limit of five knots has been imposed on certain canals, most of which are narrow and shallow, he added.
The ministry has also ordered the Phuket Marine Office to conduct safety-awareness courses for boat captains and asked operators to ensure their skippers strictly abide by the law.
“Those who defy the laws will see their helmsman certificates revoked for two years,” Mr Atirat warned.
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