Cameron Melly smashed a 31-ball 69 which included five sixes and seven fours as Ireland dominated Guernsey in their second match.
Skipper Jared Wilson scored a 12-ball 31 as Ireland made 146-5 with Forshaw taking 2-23.
In reply Guernsey had a terrible start as they were reduced 5-3 off 10 balls as Ben Fitchet and Tom Nightingale were dismissed without scoring and Josh Butler got 1.
But Ollie Nightingale and Bichard steadied the innings with a 47-run fourth-wicket stand before Nightingale went for 25.
Bichard went on to make 23 not out off 22 balls while Alex Bushell hit 16 as Guernsey ended on 74-5.
“I think it was a tough day, arguably the best two teams in the group though,” Guernsey captain Ollie Nightingale told BBC Radio Guernsey.
“So hopefully we’ll take what we learnt and get a couple of wins, or at least one win, and see how we get on.”
Guernsey face France (10:30 BST) on Friday followed by Portugal later in the day to conclude the group stage with one win likely to guarantee them a place in the play-offs.