@Aleksey ******
never saw someone get that visa from there for many many years and not without proof of funds like savannakhet will do but I see it doesn't say on their website you need proof of funds.
do remember
Vientiane is mandatory online booked appointment
They have a 3 working day processing time (example; apply Mon morning, get your passport back Wed afternoon, apply Thurz morning, get your passport back Mon afternoon, apply Fri morning, get your passport back Tuez afternoon)
Definitely post back if you go there and try and do succeed..