I will give thanks to you, O Lord, among the peoples;
I will sing praises to you among the nations.
For your steadfast love is great to the heavens,
your faithfulness to the clouds.
Be exalted, O God, above the heavens!
Let your glory be over all the earth!
David's longing was to lift up the greatness of God, to let God's glory be known all over the world. There were two ways David did this. FIrst, he gave thanks to God. This was a public acknowledgement of God's great care of him. This psalm was written while David was on the run. He was in hiding. His life was in peril. To publically thank God came at great risk. But nothing would keep David's heart from worship.
The second way in which David would lift up the worship of the Lord was through singing. David was a singer/songwriter at heart. Most of the book of Psalm is attributed to him. He worshiped through singing all his life. And he was always ready to praise God in this way. He was willing to do so publically because God deserved that kind of worship.
There were also two reasons behind this public worship of thanksgiving and song. First, David was motivated by God's steadfast love. It was greater than any human love. It was poured out to him time and again, particularly as he was on the run. It was a grace that literally kept David alive. Grace was the reason to sing.
David also was moved to worship because of God's faithfulness to him. He could not always trust any human being. He could ALWAYS trust God. God's faithfulness provided David with life, protection, and hope. David also knew God's faithfulness to Him promises. David had been anointed king. He was chosen by God and told he would be king. The Lord was faithful to keep and protect David as a result. So when David worshiped a faithful God, it was rooted in David's belief in the Word of God as true. God shows Himself always gracious and faithful. Our hearts should thus always long to see our God lifted up!