Another travel company recommendation. I have yet to research this more widely, but there is a bus Shantou-Xiamen that gets there in 3hrs flat. This is amazing, usually it takes 4, five if you get a crappy bus that circles Shantou for an hour before leaving. It leaves at 3.20pm(ish) everyday from Jinsha Dong bus station.
The company that provides this service is detailed below, with timetable. I don’t know if the other times are just as quick, but the 3pm bus always takes three hours.
I can however say that the return trip Xiamen-Shantou is nowhere near as good, they make up for being super-quick coming to Xiamen by stopping at every possible bus station, stop and layby that there is in Greater Xiamen, on the way back. So the Xiamen-Shantou leg remains at 5hrs, 1hr circling Xiamen and 4 hours on the road, no way round it.
Leave Shantou: 7.30, 8.20, 9.30, 10.30, 11.40, 13.20, 15.20, 16.40, 17.50, 19.30, 22.10
Leave Xiamen (Hubin bus station, ): 7.15, 8.15, 9.15, 10.15, 11.45, 13.15, 14.15, 15.15, 16.45, 19.45, 21.35