Yes, Swiss citizens need to show proof of onward travel when entering Laos. This is mandatory for all travelers to Laos, regardless of nationality.
A valid visa for another country, a confirmed onward airplane or bus ticket, or a letter from a travel agent confirming your further travel plans can all serve as proof of onward travel.
When you arrive in Laos, immigration officials may want to examine your documentation of onward travel. You may be refused admission into Laos if you do not have documentation of onward travel.
Here are some tips for getting proof of onward travel to Laos: