Dr Thon Thamrongnawasawat is campaigning to have tourist numbers capped on Phi Phi and other Andaman Sea islands before their natural beauty is completely destroyed.
Horrifying images are being posted on Facebook and other social media displaying the alarming problems caused by mass tourism.
With Thailand and Phuket especially attracting thousands more Chinese tourists every day, Dr Thon is making the point that the natural appeal is fast disappearing.
Economically, a few greedy people may be growing rich but their selfishness will come at great cost to Thailand, says Dr Thon, a marine biology lecturer at Kasetsart University and an established environmental writer.
He recently made the point that tiny Kai island off the coast of Phuket would be better described as ''umbrella island.''
Other environmentalists have pointed out that the prime Similan islands diving sites are also being destroyed rapidly now because of the greed of rangers who are being paid to allow illegal visitors beyond the maximum numbers permitted.
While the Similan islands shut down to recover from tourism for six months during the monsoon season, the pillaging and the profit-taking on and around Phi Phi continue all year round.
The image in the minds of many tourists of idyllic, secluded Maya Bay - made famous in the film The Beach - is far from the truth.
Speedboats ferry thousands to Maya Bay every day. Most of them are Chinese tourists, from Phuket.
Authorities kid themselves that the beauty of the Andaman is being preserved but marine surveys show the corals in ever-speeding decline.
Dr Thon says: ''Fifteen years ago, Phi Phi was among the great natural destinations. It cost 2000 baht to go visit the island.
''These days, a trip to Phi Phi costs less than 1000 baht. In five years, it will cost less than 500 baht. Goodbye, Phi Phi.''
His message and the message of others is plain: Phuket and the Andaman have the choice between the mass market and the jet-skis mentality or putting a limit on the number of visitors, preserving nature - and controlling those visitor numbers carefully.
But it may already be too late for Thailand.