You left out the important bit: Is he actually working less than 8 hour days (or whatever is the norm in your country), or is he simply working less hours than the rest of the team.
Only in the first case do you need to have that difficult talk with him. In the other case, the best plan would be to use him as an example for the rest of the team to emulate. Get your work finished and get out. If the rest of the team isn't doing that, it'll come back to bite you in terms of long term productivity and team happiness.
Only in the first case do you need to have that difficult talk with him. In the other case, the best plan would be to use him as an example for the rest of the team to emulate. Get your work finished and get out. If the rest of the team isn't doing that, it'll come back to bite you in terms of long term productivity and team happiness.