Let's analyze Paul's words carefully:
1 Thess 4:
14 For we believe that Jesus died and rose again, and so we believe that God will bring with Jesus those who have fallen asleep in him. 15According to the Lord’s word, we tell you that we who are still alive, who are left until the coming of the Lord, will certainly not precede those who have fallen asleep.
16For the Lord himself will come down from heaven, with a loud command, with the voice of the archangel and with the trumpet call of God, and the dead in Christ will rise first.
17After that, we who are still alive and are left will be caught up together with them in the clouds to meet the Lord in the air. And so we will be with the Lord forever.
18Therefore encourage one another with these words.
Paul is counting himself as part of those who are still alive at Christ's return and he is encouraging people so that they count themselves as being alive at christ's return. Christ doesn't come alone but with souls of dead believers and as Christ promised, He comes and indwells the living believers. That's how it works.
Rom 8:9 You, however, are controlled not by the flesh, but by the Spirit, if the Spirit of God lives in you. And if anyone does not have the Spirit of Christ, he does not belong to Christ. 10
But if Christ is in you, your body is dead because of sin, yet the Spirit gives you life because of righteousness. 11And if the Spirit of Him who raised Jesus from the dead lives in you, He who raised Christ Jesus from the dead will also give life to your mortal bodies through His Spirit, who dwells in you.
With the same spirit of Christ, you'll not spend more than 3 days in sheol, you will be resurrected.
1 Cor 15:
12But if it is preached that Christ has been raised from the dead, how can some of you say that there is no resurrection of the dead? 13If there is no resurrection of the dead, then not even Christ has been raised. 14And if Christ has not been raised, our preaching is useless and so is your faith.
15More than that, we are then found to be false witnesses about God, for we have testified about God that he raised Christ from the dead. But he did not raise him if in fact the dead are not raised.
16For if the dead are not raised, then Christ has not been raised either. 17And if Christ has not been raised, your faith is futile; you are still in your sins.
18Then those also who have fallen asleep in Christ are lost.
19If only for this life we have hope in Christ, we are of all people most to be pitied.
20But Christ has indeed been raised from the dead, the firstfruits of those who have fallen asleep.
21For since death came through a man, the resurrection of the dead comes also through a man.
22For as in Adam all die, so in Christ all will be made alive.
23But each in turn: Christ, the firstfruits; then, when he comes, those who belong to him.
Paul is not using future tense here when he talks about the dead being raised, he is using continuous tense- meaning that it is something that is happening even today and is on a continuous basis.
Paul goes ahead to call the resurrected believers as Christ- the first fruits (this requires wisdom). Most think that Paul telling it in a sequence form as Christ and then the first fruits and then those that are alive- nooo, Christ the first fruits is one term that means believers that die before the end of age- everyone of them is being resurrected at their own time as they die.
Heb 12:
1 Therefore, since we are surrounded by such a great cloud of witnesses, let us throw off everything that hinders and the sin that so easily entangles. And let us run with perseverance the race marked out for us,
2fixing our eyes on Jesus, the pioneer and perfecter of faith. For the joy set before him he endured the cross, scorning its shame, and sat down at the right hand of the throne of God.
3Consider him who endured such opposition from sinners, so that you will not grow weary and lose heart.