The King James Bible addresses thankfulness in several passages:
1 Thessalonians 5:16-18 (KJV)
16 Rejoice evermore. 17 Pray without ceasing. 18 In every thing give thanks: for this is the will of God in Christ Jesus concerning you.
Psalms 100:4-5 (KJV)
4 Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name. 5 For the LORD is good; his mercy is everlasting; and his truth endureth to all generations.
Colossians 3:17 (KJV)
17 And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him.
Philippians 4:6 (KJV)
6 Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.
Psalms 107:1 (KJV)
1 O give thanks unto the LORD, for he is good: for his mercy endureth for ever.