When you make your travel plan to Bhutan, you can only fly on Drukair or Bhutan Airlines which only operates a direct flights to and from Bangkok, Singapore, Nepal and India. All of the flights flying into Paro International Airport are in the morning so there is a need to stay over another country for the flight transfer. Hence many travellers or tour groups would combine the Bhutan trip with Nepal or India.
For travellers from Hong Kong or the neighboring countries/cities, Bangkok would be an easier stop over because of the abundant flight availability and it is one of the hottest travel destinations. It’s not a bad idea to get a spa and enjoy delicious Thai food before and after the Bhutan trip.