Light clothing made from natural fibres is the best clothing for the region. You will find that all hotels, no matter how small offer a laundry service or can at least arrange someone to launder your clothes for you -in many cases, this may be out by hotel chambermaids free of charge. All towns have laundry services and will usually return your clothes to you within 24 hours. Please remember that you should normally wash your own undergarments. In the rainy season, clothes may take longer to dry.
Warm clothing - for the months of December and January, a light jacket is often necessary in the lowlands - more warm clothing may be needed if travelling in the highlands. Most towns have markets where you can buy a warm jacket for a fraction of the price you would pay at home. All Mekong countries sell sarongs of some form or another that can double as scarves, dressing gowns and towels.
People in the region dress modestly. Women visitors are not expected to wear skirts, but miniskirts and revealing shorts, may often be viewed as 'not polite'. The best plan is to dress modestly like the locals.
Footwear - bring sandals or slip ons to take off easily when entering temples. Flip flops can be bought very cheaply just about anywhere.
A small collapsible umbrella is sensible for the rainy season.
A flashlight is a good idea, in case of power cuts.