You may (or may not!) remember me from mfm forum. I’m quite new here too (about 3 months) and have been mapping Sungai Petani and Seberang Perai area. Glad to see you here!
The classification is not complete, but at least there is some thing to start you off.
For kampung roads, there isn’t any classification that resembles it. For me, I use highway = living_street. The reason - it has lesser routing priority compared to highway = residential and when Mapnik renders the roads, they are shown in light grey (visually and intuitively conveys the meaning of low priority roads).
Any tag you like is available in Potlatch. Select the way. If it already has a highway tag, then edit it to say living_street. If it doesn’t already have a highway tag, click the + sign in the bottom right, then enter highway as the key and living_street as the value. But do check first that the road matches the description on the wiki for living streets: http://wiki.openstreetmap.org/wiki/Tag:highway%3Dliving_street
I have been mapping on and off around KL, Putrajaya and Bangi. My focus is on navigational utility i.e. for use with OSMand.
My way of editing is mainly using Bing map in josm, and then testing the route with routing plugin to ensure correct nodes linking, one-ways and direction.
I don’t think we have many mappers in Malaysia for OSM but having our own sub-section might start to change that