Taxi to Haad Rin

These cost 50 THB per trip, not 100 THB, regardless of the time of the month.
Always ask how much before you get in the taxi, especially if it is one of those pirates who park up outside the corner of Soi Farang or outside Yellow Cafe.
If the price is not right, counter price and if this fails just walk away, don't bother arguing for more than 10 seconds. Often they will try to get your suitcase/rucksack on the roof of the sawng tao before telling you the price. Make sure they can't get their hands on your stuff until you've agreed.