I never had to show the money... But that's pointless! 5 out of 6 russian roulette players will tell you it's safe. Most likely they won't ask, but if they do, better to have it. I wouldn't risk it, especially it's not such a big deal...
Apparently not in Vientiane... Although a guy few weeks ago on this page, said he was asked to show his bank statement. So it wouldn't hurt to have it. 20k in cash too...
You don't really need to pay someone for that... The process is very easy. Quick fly to Udon or directly to Vientiane (depending where you are), stay close to the embassy, drop you application (simple form, passport, photocopies and 1 picture) on the morning, and get your visa the following day afternoon.
Vientiane ! Je l'ai fait la semaine dernière, très fastoche. Tu te pointes avec ton passeport, et 2 photos. Tu récupères ton visa le lendemain après midi. Tu peux m'envoyer un message pour les détails si tu veux :)