I would vote no as well. I would consider it if the person was a postdoc... but a master's level lab TA? Not so much. Heck, that's what I am... and if any of my students wanted me to write a LOR, I would refuse bc I would be doing them a disservice. IMO a LOR from any instructor you took only for lab (even twice), is going to be a rather weak reference anyway, so I would steer clear of that.