Siam Winery and six other companies are producing wine in Thailand, joining winemakers in Brazil, China, India and Kenya that are challenging the dogma that wine can only be produced in temperate regions. Wines from this region of the world are possible because of advances in refrigeration and irrigation techniques, and better control over how and when vines grow.  However, Thai vintners must pay heavily for expensive refrigeration in between harvests.  In addition, Thailand is one of the most expensive places in the world to buy wine, with taxes of nearly 200 percent on locally made vintages and 360 percent on imported wine.  The high taxes are a source of frustration for winemakers, who say this has choked domestic wine sales despite a fast-growing middle class.