It's a problem of mentality of the people, like self-esteem. I can understand severely handicapped people who beg. But for people who are physically fit to work? Don't tell me you can't find work to survive in Laos. There are thousands of illegal immigrants who came as tourists in Laos and then who stay and make money.
In hardest times, some people will end up begging to avoid starvation, while others will do anything to survive, except begging. Some lazy people will beg to avoid working even if there are jobs available. Thailand is more developed and richer than Cambodia but you can see a lot of beggars in Bangkok but those beggars are Cambodians. If the Lao police will not be strict enough with the problems of beggars Laos will be flooded by beggars of all sorts (blind, without limbs, etc.. that inspire pity) not only from Laos, but mostly from Cambodia and Vietnam. These guys know where they can make money without working. In India there are communities of beggars protected by their own king and queen. Currently, Laos has enough jobs available, even though not so well paying, if you would like to have money to survive and avoid begging.