I have a four port ADSL modem/router for my CAT ADSL, but I would like to have wireless at home for my iPhone. Do I have to buy a new wireless router or can I just get a wireless access point device and connect it to one of the ports on my router? If so, where do I get it and what is the cost? Is it easy to set up?

You can just buy a wireless access point and plug it into your router, very little configuration. But since things are so cheap, you might as well buy a wireless router and bridge your modem through to that (WRT54GL, which you can install the Tomato firmware in it, a few minutes more work but very nice performer and cheap).

We have a D-Link DAP-1150 Wireless access point plugged into our office LAN, and it works fine. It will run right "out of the box" when plugged into a LAN port on your router, but will not be secure. There is an easy "browser based" administration system where you can log in and manage the access point from any computer on the LAN, to set up the SSID (wireless network name) and password.

This will be worlds easier if you aren't tech savvy type than re-configuring a new router with your ISP account details, going through the steps of upgrading firmware, bridging the modem, etc.

Or get a wireless router with built-in ADSL modem so you only have one box and everything is setup in that.

Can for example get Asus DSL-G31 for just under 2000 baht.