Asia - Required transfer time at Kuala Lumpur airport.

I need some information about the time which is required for my transfer.
I will be arriving with Malaysian Airlines from Phuket ( Thailand ) and transferring to Malaysian Airlines to Penang.
If everything is going good i should receive both boarding passes at Phuket.
I believe that both arriving and departing flights are from the main terminal.
But I do have a few questions.
Do i have to clear immigration and/or customs at Kuala Lumpur airport when i arrive from Phuket ?
And how much time do i need for this transfer ?
I arrive at 12:55 PM and depart at 01:55 PM to Penang.
Both legs are on one ticket and bags should be labeled all the way to Penang i presume.
It is my first trip via Kuala Lumpur airport and all information is welcome to put my mind at ease. ;)

Thanks for all the help.

HI Merijn, since both your flights are on Malaysian airlines, you should be able to check - in your luggage all the way till Penang and both boarding cards would be issued at Phuket itself.
You may need to clear immigration in KUL as you are carrying onto another Malaysian destination.

I found KLIA rather good airport but not so straight forward and well signed than other Asian modern airports. Are you in Y or J? You need to use the aerotrain to transfer from international to domestic and you also need to clear the immigration. This can be done rather quickly if you know where you are supposed to go. Remember to turn left when you exit the aerotrain and head down the escalators to immigration. I did go naturally to the right where everyone else was going and which had signs "immigration " etc and they said to me at the counter that you should head back right where you came from. Crucial mistake if you have tight transfer.

MH regional flights (including Phuket) use the main terminal and their domestic flights (Penang) also use the main terminal. As such, you do not have to use the aerotrain to transfer between terminals.

There are special immigration counters for those transferring between international and domestic flights, where you don't have to go landside. Usually there is hardly any queue at these counters. 1hr is a very comfortable transfer time unless your incoming flight is delayed.

If you have not paid for your ticket, it's worth looking at Firefly which I believe still fly direct from HKT to PEN using ATR70.

MH regional flights (including Phuket) use the main terminal and their domestic flights (Penang) also use the main terminal. As such, you do not have to use the aerotrain to transfer between terminals.

There are special immigration counters for those transferring between international and domestic flights, where you don't have to go landside. Usually there is hardly any queue at these counters. 1hr is a very comfortable transfer time unless your incoming flight is delayed.

If you have not paid for your ticket, it's worth looking at Firefly which I believe still fly direct from HKT to PEN using ATR70.

Mario, thanks for the information.
Firefly does not fly every day between Pahuket and Penang. ( i use Firefly to fly back to Phuket )
My understanding was also that both flights are at the main ternimal but i did not know this for sure.
Are those special immigration counters easy to find ?

The main terminal is quite straight forward, one long building with services (transfer desk, aerotrain platform, lifts, escalators etc) in the middle. Before you get 'down' to the immigration level, there is a transfer / info desk where they can give you the precise directions. Even if you miss it, I don't think there is much of a queue at the main immigration counters given your time of arrival but you will be making a long loop to the domestic departure hall.