From Songkhla city, you need to get a tuk tuk to take you to the pier, where you catch the ferry to ban hua khao. From there, you can take a tuk tuk to ko yo, if you can find one. We hired motorcycle taxis. You will recognize them by men wearing colorful vests. They drove us over the bridge to ko yo. From Ko Yo, you just try and grab a songtaew or tuk tuk heading into Songkhla town.
What a difference it makes being with a local. I'm sure that if I'd done this journey myself it would either have taken ages or cost a lot (or possibly both). However, I was in 'brain switched off and just follow the local' mode. A quick Tuk-Tuk ride took us from the centre of Hat Yai to an area where minibuses were leaving. The Tuk-Tuk fare for both of us was 20 Baht. We got into the minibus and waited for all the seats to be filled. The cost is so cheap that the drivers have to make it worth their while by having the maximum amount of passengers on board. Journey time to Songkhla was about half an hour and the fare was 21 Baht each. As the journey begins the driver passes out a small plastic basket into which everyone puts their fare.
The minibuses leave from an area at the junction of Phetkasem and Montri 1 roads. The best thing to do is get a local free map - the one that is full of adverts - and look for the Clock Tower.
The best way to get up Khao Tang Kuan is to take the furnicular. It doesn't cost much, plus your legs will thank you later.
The best way to get around Songkhla is by walking, the second is to take these large tuk tuk things. A cross between a tuk tuk and a songtaew.