I have not sat with men of falsehood (vanity),
Nor will I go in with dissemblers.
I hate the assembly of evil-doers,
And will not sit with the wicked.
And because his eyes are on YHWH he has avoided contact with all those who would seek to lead him astray. He has not sat with men whose thoughts were on what is vain and useless, on what is false rather than what is true. Compare Psalms 1:1 ‘sat in the seat of the scornful'. Nor has he gone into the houses of (or possibly ‘gone in and out with') those who hide the truth about themselves and pretend to be what they really are not (‘dissemblers'). He is straight and open and has avoided all that is doubtful and has an appearance of evil.
He hates the company of evil-doers, (but not the evil-doers themselves), for their ways bring dishonour on YHWH, and he will not sit with the wicked. While the first two mentioned were subtle and devious in their ways, these are openly and downright sinful. With ‘I hate the assembly of evil-doers' compare ‘I love the dwellingplace of your house' (Psalms 26:8). It was his contemplation of YHWH that made him turn from all who did evil. Also compare ‘in the assemblies I will bless YHWH'. The company that he preferred was that of righteous men whose hearts were fixed on YHWH.