When reading online the common wisdom was to go to Vientianne immigration early to avoid a huge line. Both this year and last year though, going earlier has made me wait longer. I'm here now and it took about 1.5 hours to get my Visa papers submitted. When I left the line was less than half as long though, massively less than the "early day line". 

 

Next year I'm thinking of going at 10am and getting it over with in 30-40 minutes. My concern is if the day I go does not fit this trend, there is a huge line, and at 11:30am they tell everyone still in line to come back tomorrow.

 

Is this what happens or do they handle everyone already in line?

It depends upon the day of the week you do the application. If you go on Monday or Thursday it will be busy since those are the days the visa run vans are there.

If you are in line at 11:30 they will process your application that day.

Go Tuesday or Wednesday at 10:00AM. No problem and you'll get your passport at 2:00PM the next day! Do not printout your Visa From The Thai Website. They will not except because it leaves the Visa Section half printed, so wait until you get to the consulate and get a form and fill out. Do not pay for the form. It's FREE! I went last week!

Edited August 31, 20178 yr by tomwct

I never understood the stupid rush to get there as soon as it opens. Remember, your hotel doesn't want to see your face before 1pm, and I can't blame them.  I cross the border at 9.30, and am at the embassy by 10.30, out by 12.00, and check into a hotel by the river at 1pm. Avoid the 'hotel near the embassy' trap, they really are sh@th@les, especially the La Ong Dao. 

As long as you will not be in a rush the day of collection, I suggest 10:30 to 11:00 as a good time. Even on a Thursday, like today, there is usually little or no line by 11:00. Recall, though, that you receive a number for collection. Applying at 11:00 will likely mean pick up after 14:30 (after 15:00 if applying on the busy days).

last time I went there I drove up Tuesday night went to the Thai embassy around 10am, small line and was out by noon.

9 hours ago, BritTim said:

As long as you will not be in a rush the day of collection, I suggest 10:30 to 11:00 as a good time. Even on a Thursday, like today, there is usually little or no line by 11:00. Recall, though, that you receive a number for collection. Applying at 11:00 will likely mean pick up after 14:30 (after 15:00 if applying on the busy days).

 

That's a really good point. If I do this I must look into a non-bus option for getting back to Udon Thani on time as the Nok Air flight leaves at 6:30pm (and the bus usually takes a little under 3 hours to get to the Udon Bus Station)

Same happened to me, went relatively early and the line went all the way to the gate , then got shorter and shorter.By 11 am it had almost disappeared.