You are flying from Dubai to Singapore, then spending a week in Malaysia, then heading to Taiwan. The trip looks perfectly logical on a map. But when someone at the first airport asks for your onward ticket, which booking should you show: the Singapore arrival, the flight from Malaysia to Taiwan, or the flight you might take home a month later?
The useful onward segment is the one that shows how you leave the country or travel area whose departure requirement is being checked. It must also fit your dates and the document standard that applies to you. The last flight in your entire vacation is not necessarily the right answer.