If the menu at Noodle Market in Arlington feels familiar, chances are good that you have eaten at Napat Sriwannavit's other Boston-area restaurants. "All of my restaurants are half Vietnamese and half Thai," says the restaurateur, describing the two cuisines as a "good mix." Sriwannavit, a Bangkok native who came to Massachusetts nearly 20 years ago, also co-owns Noodle Barn in Jamaica Plain, Beantown Pho & Grill in Back Bay, and Pho & I near Boston's Symphony T stop. When Arlington Center Thai eatery Sweet Chili closed its doors last fall, the restaurateur saw an opportunity for a fourth venture.