Some research into the verse showed that in this verse, the word thanks comes from the Greek word eucharisteo, which means, “to give thanks.” The Greek root words for eucharisteo are eus, which means to be well off, fare well, prosper; acting well, and charis, which means, grace; that which affords joy...favour, of the merciful kindness by which God, exerting his holy influence upon souls, turns them to Christ...
Eucharisteo is all about God saving us. Eucharisteo, the thanks in 1 Thessalonians 5:18 is giving thanks to God for His salvation – in every thing. Regardless of what happens, it is God's will that we continually thank Him for salvation.
Why is it important that we keep thanking God for salvation?
One reason is that thanking God for our salvation keeps us in perspective. When we think of our salvation, we should be reminded that it is a gift; we don't deserve it. None of us. It is easy as humans to classify sins and make our sins little in light of another's sin. But all sin leads to death. While there are sins that have more impact here on earth, in God's eyes, all sin results in a burden of debt that we alone cannot pay. As a society, we classify sins by severity in order for our imperfect world to function. But God needs no such coping device; He is so Holy that all sin is an affront to Him.
Another reason we should keep thanking God for our salvation is because of the joy that doing so brings us. Who can sing a song such as “I Stand Amazed” or “Wonderful Grace of Jesus” without feeling the joy of the song well up within the heart? Such songs have lyrics that remind us of what was done for us and bring to mind that we are freed from our wretched state. The heavy burden has been taken from us and borne by the only One who can truly carry us.
I found it interesting that in this verse, there does not seem to be a command to thank God for every thing that happens to us. Rather, judging from the word used for thanks, it appears that we are told to thank God for our salvation, even when bad things are happening. When I am confronted by something I do not like, I should not allow the bad to distract me from the good. My present circumstances should not keep me giving thanks for what has already been done for me.
Now that this subject has been brought to my attention, I plan to research this topic some more.