Ten Hag revealed he had a conversation with Ronaldo before news broke that the 37-year-old wants to leave Old Trafford this summer but said the pair have not spoken since.
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Ronaldo has been granted time off to deal with a family issue and has not travelled to Bangkok ahead of the first game of the preseason against Liverpool at the Rajamangala National Stadium on Tuesday.
"He's not with us and it's due to personal issues," ten Hag said at a news conference Monday.
"We are planning for Cristiano Ronaldo for the season and that's it. I'm looking forward to working with him. I have read [that he wants to leave], but what I say is Cristiano is not for sale, he is in our plans and we want success together.
"I spoke with him before this issue came up, I had a conversation with him and I had a good talk. That is between Cristiano and me, what I can confirm is we had a really good conversation together."
Ten Hag has arrived in Thailand with Tyrell Malacia as the only new signing in the squad.
"We know what we want," ten Hag said. "We not only want new players, we want the right new players. "We have a good squad, there's huge potential, only when we find [the right players to make] an improvement in our squad we will do [it].
"Definitely we are searching for players in midfield. We have a need and we are still looking for players.
"It's going to be a long season but a season that is quite unusual due to the World Cup, so you need to be prepared for this and need more players than in a normal season."
Ten Hag also confirmed that Harry Maguire will remain club captain.
"I have to get to know all of the players, and that takes time, but he has been captain for years," he said. "He has achieved a lot of success, so I don't doubt this issue."
Maguire is training away from the main group because of a minor injury.