Is pretzels pas habaah bicisnin?
Yes, pretzels are pas kisnin, and their bracha is mezonot.
In order to qualify as Pas Haba Bikisnin [snack like bread foods on which the bracha is mezonot as opposed to hamotzi on regualr bread] one of three criteria needs to be met: the dough has a filling, the dough is needed with things other than water [sugar,oil,milk etc.], or the dough is made into a crispy, crumbly texture, see Shulchan Aruch O:C 168:7.
Pretzels fulfill the third of these criteria and therefore are certainly mezonot.
Generally the rule for the above is that if one eats enough that they are serving as a meal, he would treat them as bread and say hamotzi and birkat hamazon. However this requires that the food maintain “tzurat hapas” the shape and look of what people would consider resembling bread, see 168:15. Many poskim are of the opinion that pretzels would not qualify as tzuras hapas, and as such would be a mezonot even if eaten in large quantities.