Ronaldo has reportedly told the United hierarchy he wishes to move on should they receive a suitable offer this summer.
The 37-year-old has not reported for pre-season training and is not part of Manchester United's travelling party to Thailand.
Ronaldo scored 24 goals in all competitions for United last season after returning to the club from Juventus for a second spell.
Questions have been asked about Ronaldo's suitability to Ten Hag's system but the former Ajax Amsterdam boss is eager to have a five-time Ballon D'or winner to call upon when necessary.
"So, he's not with us. That's due to personal issues," Ten Hag said in a news conference ahead of a meeting with rivals Liverpool in Bangkok.
"We are planning with Ronaldo for this season – that's it. I'm looking forward to working with him.
"He hasn't told me [he wants to leave]. I have read but as I say, Cristiano is not for sale, he's in our plans and we want to get success together.
"I spoke with him before this issue came up. I had a conversation with him and had a real good talk."
Ten Hag also confirmed Maguire will continue in his role as Manchester United captain next season after his leadership qualities came under scrutiny in a difficult 2021/2022 campaign which ended in a disappointing sixth place finish.
"Harry Maguire is the captain," he said. "Of course I have to get to know all the players but he is the established captain and he has achieved a lot of success."
