best way from ko phi phi to perhenthian islands?

Getting to the Perenthians from anywhere in Thailand is pretty awkward, but you've obviously looked into it and although Penang would seem to be a bit of a roundabout route it may be the best way. I'd say you could get to Kuala Besut before 4.00 pm, which is when I think the last boat goes, but you'd have to depart from Penang pretty quickly after getting there. If you can't then Georgetown is a great place to spend a night, then head across the next morning. In fact I think that's what I'd do.

Any travel agency on Phuket can book you a seat on a mini van going to the Malay border on that coast. A matter then of crossing the border and getting a bus to Kota Bharu. No need at all to go to Penang.

That's a long haul overnight in a van though, followed by a lot of faffing around on the Malay side. I wouldn't fancy that in one go. A stopover would make more sense, maybe in Had Yai rather than Penang.

No, should be one that leaves early in the morning.

Bus to Hatyai, then PUBLIC minibus leaving constantly when they are full to the border above malaysia.. Cross over to KB and one night in Kota Bahru if necessary.... Easiest to arrive in the morning into perentians....Cut the trip into 2 and have a good nights sleep!! Great markets in KB

Thanks for all the advice. If I do go via kota bahru does anyone know if there is an atm there? I heard that the islands and Kuala besut don't have any
Thanks

KB is a city and the capitol of Kelantan state. You can expect most of the facilities of any city in Malaysia.

Remember even if you were going as the crow flies from Phi Phi this is a journey of HUNDREDS OF KILOMETERS !!!! . And if you went via Penang you have to go on a windy mountain road journey that consumes most of the day .
As suggested go to Hat Yai , from there its about 3 to 4 hour journey to Sungai Golok. Its about one kilometre walk to the Malaysian border town of Rantau Panjang and from there you can get share taxi for the 50 km journey to Kota Bahru. Yes you do have to get some some cash for the islands , and ATMs are available in Kota Bharu , banks charge high commission for changing travelers checks. From Kota Bahru its another 50 kms to Kuala Besut and then a 20 km boat trip out to the islands. So you can see this is a long trip .

Just to add , the bus to Penang would actually go to Butterworth , and for that matter thats where the buses to Kota Bharu leave from . Just for referenceif you ever wanted to travel from Thailand to Penang /Butterworth theres no need to take a direct tourist bus . Cheaper and more flexible just to take local transport to Hat Yai cross the border yourself then take local transport the other side to Butterworth.