Is it difficult to buy a ticket from Hualien to Taipei Main Station? Going in mid-May, do I need to buy online in advance? Or is it available now?

Taiwan Railway tickets can be booked online 15 days in advance. Whether you need to book in advance depends on whether you are in time for the holiday in Taiwan. If you catch up, it is best to book in advance, as long as you do not have requirements for train numbers, time, and whether there are seats. available on site

It is not difficult to buy, and the passenger flow of Taiwan Railway is not particularly large. Of course, if your itinerary is determined to remain unchanged, it will be more practical to buy it in advance.