How recent must my bank statement be when applying for a visa at the Vientiane consulate?

You can use statements on the day. It's more important to show how long the money has been in the account. Some require 3 or 6 months

When you post something like this, it's best to provide a little more information, at least which visa you're applying for, sometimes your passport country otherwise there may not be enough information to provide you an answer.

I'm going to guess that you're applying for the Destination Thailand Visa because you're asking about bank statements. While I can't be 100% sure, as it's not a something I'm looking at right now, from reading other posts, I think your bank accounts need to be no more than 7 days old when applying. I'm only responding because nobody else has responded after 7 hours of you posting your question. Have you tried asking the Consulate? Have you tried searching within this group for the answer? If not, click the 'magnifying glass' and type in something like 'DTV, bank statement'. You should get some posts appear, then read through those posts and hopefully you'll get an answer from someone who's asked the question or provided information on the subject.