First of all, Viet-Thai is the best Vietnamese food in Lowell. (And if you're going to wear us out with platitudes about Pho 88, all I can say is that you haven't had real Vietnamese food yet if that's your standard, and I'm not saying Pho 88 isn't great--it is). Second of all, for whatever reason they went in with the Lowell Sun on a "SunDailyDeal" (http://www.sundailydeals.com/) that offers $16 worth of food for $8. (Maximum two per customer). Second of all, if you're going to max out your allotment, bring at least 3 or 4 friends, because $32 takes you a LONG way at Viet-Thai. (When you consider you can get it for $16, the deal instantly becomes "must have").
You can not go wrong anywhere on their menu. I like their spring rolls, (translucent, minty fresh and sublime with their peanut sauce), their fried squid, (so lightly breaded and deep fried, and fresh and tender), and their Pad Ke noodles, (with beef, but you can pick your protein), but I have friends just as rabid about their Tom Yum soup and Pho across the board. You can bring your own bottle, but don't miss the shakes for a sweet treat while you're there.
Can't say enough good things about this restaurant, and at half price it's ridiculous.
1270 Westford St, Lowell, MA 01851
368 Merrimack St, Lowell, MA 01852