Thai coffee is having its moment, with demand for specialty local beans surging. But the industry faces multiple challenges including poor yields due to climate change, rising costs and intense competition.   CHIANG MAI: As mist rolls in along a mountain ridge high above Chiang Mai, Chatree Saeyang climbs up steep wooden stairs to his rustic village cafe, a hideaway in the clouds for coffee drinkers. Chatree, 39, is a third-generation farmer and a tinkerer. Littered behind the cafe counter is