hammer-on pull-offs

okay, so heres a thing I really do want to know. When use hammer-on pull-off technique and u must place your hand on different frets subsequently, do u pick more than once? I'll make more clear.
in this part, do u have to fret the string after you have had hammered on the 14th fret and then pull-off to the 12th fret, or in the whole process u should pick just once, just tap normally ???

The notation implies that you hammer on to 14, pull off to 12, and then hammer on to 15, so you would pick just once. How you play it, however, is entirely up to you.