technocracy

The answer is unlimited - just the costs of the visa and renewing your passport basically every year when full (a Lao Visa takes up a full page plus the Thai stamps) . . . you can however extend a 30 day visa to 90 days if you can stay for 90 days at a time.  This can be done by a visit to the immigration office in Vientiane (although you'll need to speak Lao to do that) the alternative is use an agency who'll you have to pay to do the leg work.

Sorry I've not been around - been somewhat busy - anyway the 12 month 'work' visa which I have previously mentioned I arranged via a Lao friend who knows the immigration system but it is based upon being married to a Lao citizen.  

Basically the visa allows you 30 days stay at a time over the 12 month period - but you can come and go as many times as you wish i.e. Full multiple entry.  It worked great for me as we'd often nip over to Udon or Nong Khai every month for shopping and the like.  

The visa is actually intended for people who have business interests in Laos and will come and go frequently - but they will also do one if you are married - in any case if you work you are liable for sorting out your own taxes etc.

The alternative is to get a work visa sponsored through an 'agency' - this will end up with you paying 10% tax of whatever your declared salary is - a word of warning on going down this approach the Lao government has cut back on the number of sponsored foreign employees and your work visa probably will end up being assigned to some non-existent NGO or one that is based in distant rural areas.  If you have any kind of run in with the police (simply driving down the road can cause this!) they will check your visa and the 'company' you 'work' for and you can end up in prison if they find out it's a visa of convenience and before you all start saying it doesn't happen etc etc.  Well I know 2 people who have fallen foul of it . . .