I notice the lads borrow someone's speedboat and go belting down the much-fabled Chao Phraya River in Bangkok and in about one minute of screen time are suddenly surrounded by the beautiful emerald waters of Krabi with its signature limestone upthrusts.
Attention Hollywood: that is NOT possible!
You see, the Chao Phraya feeds out below BKK into the Gulf of Thailand. A quick glance at a map tells me that is on the opposite side of Thailand's land mass from Phuket, Krabi, etc.
They would then have to go down the length of Thailand, past Hua Hin on the right, Pattaya on the left, past Koh Samui, reach Malaysia's east coast, keep going, chuck a right at the Singapore straits, cut through to Malacca and up the western side of the Malaysian peninsula.
Eventually they would go past Langkawi in north-western Malaysia before reaching again the waters of Thailand around Phuket after around 3,000km of sea travel.
By my SWAG method of estimation (Scientific Wild-Assed Guess) that would take more like 4 or 5 days at quickest, and several petrol stops, meaning the lads would have missed the wedding, jing jing.
Sorry to be so hard on an American B-movie (which I actually enjoyed a lot), but I haven't forgiven Hollywood for it's far-fetched fictional treatment of The Bridge on the River Kwai yet.
There are much quicker ways of getting to beautiful Krabi, of course. You can always fly, or take a car or bus.