How this corona-crisis situation might affect on getting Thai visa if I plan to go there in Dec? 

It is absolutely and totally impossible to predict today what the situation will be in December.

Yes, exactly, thank you for the answer. I already cancelled the trip. Next time I will try to predict any circumstances. Anyway, if I arrive there, what would be the safest way to get to the hotel from the airport?

12 minutes ago, 1submarine said:

Yes, exactly, thank you for the answer. I already cancelled the trip. Next time I will try to predict any circumstances. Anyway, if I arrive there, what would be the safest way to get to the hotel from the airport?

Private helicopter or self driving Tesla.

There is a fair chance that you will have no problem coming in December. We will know a lot more in the next few months.

42 minutes ago, 1submarine said:

Yes, exactly, thank you for the answer. I already cancelled the trip. Next time I will try to predict any circumstances. Anyway, if I arrive there, what would be the safest way to get to the hotel from the airport?

Depend where is your hotel? In soi 11 or in Chiang Mai! Other one cost "little" more whit taxi!

1 hour ago, 1submarine said:

what would be the safest way to get to the hotel from the airport?

taxi. make sure they turn the meter on or don't go.

taxi using the Grab app from other locations except the airport.