The Chief of Marine Office 5, Phuripat Theerakulpisut, said today: ''Random checks will be made and any speedboat where the captain does not ensure that passengers are properly protected will face severe penalties.
''They could lose their livelihoods.''
The upgrade in regulations follows the drowning of two Indian passengers when a traditional longtail boat was swamped off the coast of Krabi earlier this month and the deaths of two Koreans when a speedboat laden with passengers flipped on striking an anchor rope or net while returning to Phuket from Phi Phi.
The captain of the speedboat is in jail in Krabi - the crash occurred in Krabi waters - and is facing serious charges.
Police are waiting for the captain of the fishing trawler involved to return so he can be interviewed before proceeding with the case.