You can see pink dolphins in Thailand, near Koh Samui, Surat thani and Nakhon Si Thammarat.
This is an ethical wildlife encounter as the pink dolphins in Thailand are wild and free to swim. They are not fed and they live locally in these waters.
For the pink dolphin trip, I recommend booking through your hotel. If you are lucky or in a group, there is a full day trip costing around ~1000 thb that includes dolphin spotting, waterfalls and some small island exploring and lunch.
These pink dolphins are a sub-species of white Chinese dolphins. It is thought there are around 150 in Thailand.
Disclaimer: In all honestly, ALL the dolphins did not look SUPER pink to me like the one shown. It is rare to see one this pink.