My daughter traveled to Europe on her German passport. (she also has a Thai passport).

Her German passport has expired (March 2019) and she needs to return to Thailand.

Will this present a problem for her to leave Europe?

She can not renew her German passport in Germany (long story). She must return to Thailand.

Erm, no.  Leave on Thai passport.  

 Leave on Thai passport.  

BUT they will look at the Thai passport and say"How did you get here?"

8 minutes ago, bikerlou47 said:

BUT they will look at the Thai passport and say"How did you get here?"

Hand over both passports - job done.

The only problem could be if the names on each passport don't match. If they do, no real problem. 

names match just that the German passport has expired.

I hope you guys are right! LOL

 

Thanks so much

1 minute ago, bikerlou47 said:

names match just that the German passport has expired.

I hope you guys are right! LOL

 

Thanks so much

No problem and 100% there'll be no problem.  What are they going to do, send her to Stalag Luft III?

She will certainly be questioned so she should leave plenty of time.

She should leave Germany on the passport she entered in, but as that passport is no longer valid for travel she can't, though it is proof of citizenship, which doesn't expire, even if the passport has.

If she leaves with just her Thai passport she will most certainly be asked when she entered and why she doesn't have a visa, I'm assuming there's no entry of her arrival in her German passport.

 

Maybe your daughter should call the Bundesgrenzschutz at the airport from where she want to leave. 

https://www.bundespolizei.de/Web/DE/01Sicher-auf-Reisen/06Passrechtliche-Hinweise/01Ersatzpapiere-beantragen/Ersatzpapiere-beantragen_node.html