Cross the Malay Peninsula at its narrowest point — just 44km of land separate the Gulf of Thailand from the Andaman Sea. Highway 4 runs from Chumphon over the low spine of the Kra Isthmus and down the Pakchan River estuary, with Myanmar on the far bank, to Ranong — Thailand's wettest, least-touristed provincial capital, famous for its geothermal springs. An easy, atmospheric sea-to-sea day.
Clone it to your planner, customize dates and stops, then ride. All free.