It depends on the context. If the focus is on "pandai" then write it first, vice versa.

There are no strict rules to place the adjective at first, despite their positive or negative meaning. It depends on the context or the previous sentences before it. If the previous sentences said or explained about 'pandai' then put it first, then followed by the second adjective, 'malas' which, contrary different with the first adjective to make a contradictive perspective.