Thomas aquinas had allot to say so I may not be able to answer your question unless you specify. You might want to know what he thought about foreknowledge. Accoringing to his thoery on foreknowledge he believed that God's will reigns supreme and therefore all things pertaining to future events have already been considered and implemented before the creation of the universe. Beilieving that God is timeless he also follow aristotles assumptions. Those assumptions that follow would be that God is immutable and impassable. Because of these assumptions it would follow that there could never be any sort of change in the godhead. God is perfect as he is in his timeless state and any kind of change would only be change for the worse. Implict in being a changeless being implies an inability to relate to creatues like ourselves in any so of real relational way. He would have to stop as it were from being in a timeless static state and listen or relate to us and this would imply a move from timelessness to temporality. Because Aquinas saw God as such he believed it was necessary for god to determine all future events including all our future free-will actions. An example of this would be as follows; Suppose you wanted to pray to God for something you wanted him to do for you or someone else. Aquinas belived that the very prayer that you pray was ordained before the creation of the world so that you would not be forcing god to stop being timeless because that would require him to stop and listen to your prayer thus changing or interupting his static blissful state. Remember God is impassable which defined means he cannot relate to us in any way. You would therefore be praying a prayer he determined you would pray and so it would be an answerable prayer in that way. Theres more to this and I hope I have sparked some interest for you.
Mike