If I go to Taiwan, enter from Taipei, and depart from Kaohsiung, can the ticket of the same airline be counted as a round trip?

Are you referring to booking tickets on Ctrip? That is not possible, but when you go to the airlines to book tickets, they have the opportunity to use round-trip package pricing, depending on the marketing strategy of individual airlines. For example, Cathay Dragon Hong Kong and Taiwan have such discounts.

You can only choose a round trip if you enter and exit Taipei and the same airline. If you enter Taipei and exit Kaohsiung, you can choose multiple journeys when booking online. Remember to print the ticket after purchasing the ticket, and then go to the designated counter of the airline to print the ticket after arriving at the airport. Hope to help you, welcome to adopt.