some Amphurs offer the translation and certification by the MFA for an added fee. This service is worth the 1500 baht I paid for it. We went into the Amphur, met with the woman who handles marriages, she reviewed the paper work and told us to come back in 2 days. When we came back all the paperwork was drawn up, we signed and thats it..
You can do the Multi non immigration one, after 90 days simply apply for a 60 day extension which gives you 120 days without a border hop. The visa can be obtained in your home country as well as Laos.
You can turn up in the country on any visa or visa exempt, get the freedom to marry paper from your Embassy, have your passport translated and certified from the MFA, then turn up at your local Amphur and get hitched.. all can be done in less than a week (took me 3 days).