Arriving at Butterworth by bus you’ll end your journey at Penang Sentral. Penang Sentral is a hub from which you can catch the train, bus or ferry.
From Penang Sentral there is a train service north to Padang Besar on the Thai border. You can cross the border to Thailand at the station. From there you can transfer to trains travelling north through Thailand. Or you can cross the border at the road crossing and catch buses to other parts of Thailand.
Alternatively, arriving at Butterworth by bus, you can catch other buses to various parts of Malaysia from Penang Sentral. Finally, there is a ferry service four times an hour, across to Penang Island, a 15 minute journey.