Should I dress formally when applying for a non-B visa at the Thai consulate in Vientiane?

I just received a visa from there 2 weeks ago. There are signs up that say, "Please dress respectfully." Many people were there in shorts and tank tops.

There are also notices that say, "You must have an actual street address in Thailand. "

I saw a sign that said that, and a paper with my queue number said that.

Having your paperwork in order is more important, but don't go looking like you crawled out of the sewer either.

A 3 piece suit is highly recommended

Id be more worried about making sure you have all the correct paperwork

by the way do they ask tickets from TH to third country?

Conservatively, not formally. As long as you don't look like you just arrived from the beach or Khao San Road…