I cannot speak on the reliability of the information provided, but the site below purports to list Kota Bahru busing options — click on the logo:
Wikitravel claims: …The buses to Penang (RM34.70, six hours and 15 minutes) with one long stop (60-75 minutes) at Gerik. Buses to Penang leave in the morning at 9 am and in the evening.
IgoUgo adds: Excellent network of long distance bus services – but advisable to reserve seats in advance – especially for the journey from Kota Bahru to Penang.
Kota Bahru, Kelantan Malaysia (Jan 2009)
Uploaded by fishman25 on Jan 23, 2009
Kota Bahru is the capital of the state of Kelantan on the eastern coast of peninsular Malaysia. It is 6-7 hours to travel by bus from Penang or Kota Bharu’s small but efficient Sultan Ismail Petra Airport (KBR) in Pengkalan Chepa currently receives flights from Kuala Lumpur (provided by Malaysia Airlines and Air Asia), and Johor Bahru (provided by Air Asia). Advance bookings especially for Air Asia can be very cheap. The airport is 15 minutes from the city centre by taxi. You can also catch an SKMK bus from the local bus station in the city centre. A friendly, cheap, clean and safe guest house located in the city centre. Only a two-minute walk from the bus station. Backpacker’s inn will cost between RM15 to RM25 and the budget hotel there is between RM35 to RM80.
Kota Bharu is a very socially conservative city in a state ruled by the Islamic Party of Malaysia (PAS). Be respectful of the cultural and religious sensibilities of its primarily Muslim inhabitants. There is no need for non-Muslim women to wear a tudung (kerchief over the hair), but both men and women should consider wearing proper clothing. Tourists dressed in shorts and skimpy shirts seem out of place on the East Coast of Malaysia.Don’t bother to look for the night life entertainment place here because the Islamic party run the state government has banned the sale of alcohol in the state resulting in ending what little nightlife the city had before. Nevertheless if you really need a few beers, you can get it from the little China Street while dining there.For many visitors it is a stop before heading on to Thailand. Border crossings Thai/Kelantan are at 1-Buketa/Bukit Bunga, 2-Sungai Golok/Rantau Panjang and 3-Tak Bai/Pengkalan Kubor. Golok border close at 10.00pm and the rest close at 6.00pm. Bus ticket cost only RM5.00 from Kota Bahru to Rantau Panjang border.