"I exhort therefore, that, first of all, supplications, prayers, intercessions, and giving of thanks, be made for all men;For kings, and for all that are in authority; that we may lead a quiet and peaceable life in all godliness and honesty." -- 1 Timothy 2:1-2
That is Paul telling us to pray that men to come to a saving faith in Jesus Christ and reminding us to give thanks always for God's grace.
It does not say to pray to anyone but the Triune God of creation.
"Shall I fall down to the stock of a tree?"
If in Timothy's church an intercession is made, say, for a king, then Timothy is praying to Christ on behalf of the king. Christ is mediator, Timothy is intercessor, and the king is the benefactor.
If a king came to Timothy and asked Timothy to pray for him, that then would be entirely biblical, because this would be exactly what the scripture tells Timothy to do.
If Timothy were to die, and go to heaven, Timothy could continue doing the same thing. That is because Timothy would then receive eternal life promised him in 1 Timothy 6. But now the king would be praying to St. Timothy, would he not?