I wasn't sure about the rules, so I had to find out.
Yes, a Designated Hitter (DH) can play a defensive position later in the game, but doing so forfeits the team's DH role for the rest of the game.
It's kind of funny, or I should say interesting. When we saw the Cubs schedule, when the season started, we thought Phillies - Mets - Phillies - Dodgers - Padres would be really tough. So far, so great.😄