R.O. Means Reverse Osmosis. PWA Samui and PWA Phuket using R.O type SWRO (Sea Water Reverse Osmosis)

Because Fresh water and reservoir for process water supply system not enough at Samui Island and Phuket Island.

I think so with your opinion

"the problem is: to supply drinking water to people 500+ Km from the sea, no electricity, no money."

PWA solve a problem by connect pipe line around Island and using pump station feed to high tower for supply.