Karin Adam, Although I do not know the answer to your question... First, check with your own embassy there in Germany. Next you might try the German embassy in Thailand. It is your embassy's job to keep up with the current situation globally as it pertains to assisting their own citizens traveling abroad--which includes travel advisories, recommendations, consular help, and emergency assistance. It would benefit you to register with their ‘citizen traveling abroad’ program, as they will regularly email and update you about changes as they take place in the region(s) where you ibtend to be.

Currently (but may change accordingly), the international travel ban to Thailand for foreigners is scheduled until May 31, 2020--but is subject to change. If you want to know the latest policies taking effect, you can watch PR Thai Government’s Deputy General who give a daily English summary of the cabinet meeting, ministers and officials reports, in which the proposals, votes, and regulations are announced each day, in addition to the Covid-19 status report.

DHL delivered my package from USA to Bangkok yesterday. It took 1 weeks to clear customs after arriving in Thailand—instead of anticipated next day delivery. But it arrived...though pricey to mail and also had to pay import duty.