Pol Capt Sophon Khongthong of Krabi Police said officers received a call at 3:30 pm. When they arrived at the scene they found the badly damaged speedboat Chainath Nam Chok 8, owned by Barracudas Co, half-sunk close to the shore.
There was no sign of the hotel boat, belonging to the Centara Grand Beach Resort & Villas Krabi.
Two of the injured tourists were hurt seriously enough to be taken to Krabi Hospital. They were named as Jens Jorgen Andersen, 27, from Denmark, received chest injuries while his four-year-old son Anton, suffered leg injuries.
Speedboat driver Sorrasit Haempithak told police he was on the way from Phi Phi to Ao Nang at high speed with 27 passengers on board.
The Centara boat, driven by Anant Khaothong, came out from the pier at Noppharat Tara, taking 10 hotel guests and crew to Pai Plong Bay, the site of the resort, which is difficult to reach by land.
As he motored parallel to Ao Nang beach, the Barracudas speedboat T-boned the Centara boat, sending it to the bottom.
Chaos ensued as the Centara guests floundered in the sea and were joined by passengers from the speedboat, which was also taking on water fast. Luckily the collision was close to the beach where it was seen by many people.
The alarm was raised and a patrol boat from the Krabi Marine Department was quickly on the scene, rescuing all.
While the wreck of the hotel boat was marked so that no one else collides with it until arrangements can be made to salvage it, police took Sorrasit and Anant to the police station to see if they can figure out who was to blame.