A man to whom God hath given riches, wealth, and honour, so that he wanteth nothing for his soul of all that he desireth, yet God giveth him not power to eat thereof, but a stranger eateth it: this is vanity, and it is an evil disease.
He wanteth nothing for his soul - i:e., for his enjoyment.
Yet God giveth him not power to eat - through the avarice which enthrals him. This distinguishes him from the "rich" man in Ecclesiastes 5:19. "God hath given" distinguishes him also from the man who got his wealth by "oppression" (Ecclesiastes 5:8).
But a stranger eateth it - those not akin, nay, even hostile to him (Lamentations 5:2). He seems to have it in his "power" to do as he will with his wealth, but an unseen power gives him up to his own avarice. God wills that he should toil for "a stranger" (Ecclesiastes 2:26), who has found favour in God's sight.
An evil disease - as fatal to happiness of the soul as a severe sickness is to the ease of the body (Deuteronomy 28:59).