About the Visa on arrival, I just want to add that travellers holding passports from the below list of countries are not eligible:
Afghanistan, Algeria, Bangladesh, Burundi, Cameroon, Congo, Cote d’Ivoire, Ghana, Guinea, Guinea Bissau, Jordan, Lesotho, Liberia, Libya, Mozambique, Nauru, Niger, Nigeria, Pakistan, Senegal, Sierra Leone, Sri Lanka, Suriname, Syria, Swaziland, Tonga, Turkey, Zambia and Zimbabwe.
If your passport is from one of the above 29 countries, you will have to visit an embassy before entering Laos
You can always find an updated list of which countries are eligible for visa on arrival (and which are not) over here: http://www.tourismlaos.org/show.php?Cont_ID=348
Have a safe trip!