Malaysia:
From the airport, train station and city you can take a taxi to Kuala Besut for ferry connections to the Perhentian Islands 45-60 min; theoretically only RM80. If you want to stick to public transport, there is also a direct bus service to Kuala Besut, take the bus 639 from the central station (6RM, the trip takes 1h30m and they have service leaving at 6h15,7h30,9h00,10h00,11h00,12h30,14h00,15h00,16h00,17h30,18h45
Thailand:
Sungai Kolok
Tak Bai via Ban Taba