meaning of "to be intentionally thick"

Solution 1:

Thick (colloquial) = stupid.

OED:

9b. Of mental faculties or actions, or of persons: Slow (or characterized by slowness) of apprehension; dense, crass, thick-headed; stupid, obtuse. Now chiefly colloquial of persons. Also emphatically, as thick as two planks, etc. Cf. thick-headed adj.

1603 J. Hayward Answer Conf. conc. Succession iv. M j I omit your thicke error in putting no difference betweene a magistrate and a king.

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1974 G. Honeycombe Adam's Tale i. ii. 27 ‘He must be as thick as two planks,’ said Nick.

1976 J. I. M. Stewart Memorial Service iii. 40 You might expect to become P.M. if you hadn't been so thick as to accept your idiotic life peerage.