Well, I started researching this topic in full detail this morning. Including Rev 5:8-10 and Rev 14:3. The short:
Rev 5:8-10 was a song sung by the four living creatures and the 24 elders, so it was not the same as the song sung by the 144,000 in Rev 14:3 where they sang before the throne and before the four living creatures and the 24 elders. Two different groups of singers.
Rev 5:8-10 talks about persons bought for God. So, that led me into who was "bought" or "purchased". Yes, the 144,000 were bought. (Rev 14:3) Both 1 Cor 6:20 and 1 Cor 7:23 say, "you were bought with a price". So, who's the "you"? Who was Paul writing to? 1 Cor 1:1 says: "to you who have been sanctified in union with Christ Jesus, called to be holy ones, together with all those everywhere who are calling on the name of our Lord Jesus Christ, their Lord and ours." So, everyone calling on the name of our Lord Jesus Christ. Acts 20:28 talks about shepherding "the congregation of God, which he purchased with the blood of his own Son." So a lot more than just the 144,000 were "bought".
Based on this, Rev 5:8-10 could very well include way more than 144,000. There is no direct link between 144,000 and those who serve as kings for 1,000 years in the Bible. The link just does not exist. Any link produced is pure speculation.