Three locations, one an actual restaurant on Sukhumvit between Soi 12-14, next door to Times Square. The other two are mini-eatery style in the basement food level of Siam Paragon and on the fifth floor of the Emporium.
The only one I've been to is the basement of the Siam Paragon. The office had ordered for cater in a couple of times. I feel like the catering is better than the eatery. Not necessarily because the food is better. The selection in a cater menu is limited, but they do the limited menu well. They make nacho plates, burritos, and quesadillas on the spot, using a decent selection of fresh ingredients. The one thing wrong with their nachos is the cheese tastes like Velveta variety instead of proper melted cheese. Their ingredients include a delicious mucho mango sauce that is just a different spin to the salsa option and I need to find out the recipe for that.
They scratch my guacamole craving. That, to me, is the most important thing when going for Tex Mex. The food isn't bad as eating Tex Mex goes in Southeast Asia. Given a tiny bowl of guacamole goes at a hefty cost of $5, I usually order a platter than includes guacamole. The plates, averaging at 200 baht ($6) include combinations carrying an American serving sizes of tacos, enchiladas, burritos, quesadillas. A fajita will set you back $10.
The menu indicates either an American created it or that they confuse Mexico with USA (even though Tex-Mex is arguably American). Features order is "USA Cowboy Tacos" and a following description of "Three crispy Tacos stuffed with seasoned ground beef, cheddar cheese, lettuce, onions and fresh tomato salsa. Served with Mexican rice and red beans." Desserts are "Homemade Apple, Pumpkin or Key Lime Pie" and available in "You so GOTTA try! Slice" or a whole pie ($10!).
Verdict: they are OK. Makes for a filling cater lunch, but not worth trip to the eatery. I will have to try the restaurant for a more complete assessment, otherwise I'm moving on the the next attempt of a Tex Mex restaurant offering. Unless I want the mango sauce. That is just a unique offering appropriate for the location.