Shia LaBeouf Jokes with Older Woman

Shia LeBeouf got hitched to Mia Goth in Vegas Monday, but just a couple days before ... he was lit up and in love with another woman in Germany.

Witnesses at the Frankfurt Airport bar tell TMZ ... Shia was super friendly with other patrons and even bought a round of shots for everyone. He especially took a shine to an older lady in the bar ... and had some fun when she walked over to say goodbye. Weird fun.

Check it out ... Shia turned on the charm big time, saying he wanted to follow her "into the future." Everyone got a laugh, including the woman ... who had her own witty comeback for him.