It is the other way around!

In Eph 5 verse 18, we have this portion where we are exhorted to be filled with the Spirit and then Paul writes about what it implies. We are to sing and make melody and be thankful. Now this singing etc, is the evidence not only of being filled with the Spirit but also being rich in His Word as mentioned in Col 3:16.

First of all, I want you to observe that the 'filling' mentioned here is not the same Greek word for 'being filled with the Holy Spirit' and empowered as mentioned in the book of Acts repeatedly. So this filling is more of a rich experience in the Spirit rather than being empowered to heal or deliver or any such. It is more of being full in proportion rather than filled to perform.

Secondly, the usual flow of thought when we read that portion in Eph is that the singing happens because we are filled from above. My contention is that since it is mentioned in Col too, the singing is not the evidence of being filled. We have to see it the other way round. When we sing and rejoice and have a thankful heart, we are actually moving towards a fuller experience in the Spirit. We are allowing Him to fill our lives. And so it is with the Word of God as well. When we use the psalms etc, and begin to admonish one another, we are allowing the Word to richly dwell within us. This is not a intellectual knowledge of the Word of God but rather, a rich active movement of the Word of God in us.