What are the best times to visit Chang Wattana for visa services to avoid long waits?

Well the good news is you'll get served because you have a queue number

BUT

That was a near total fail showing up on a MONDAY this late in the day.

If you'd have shown up at say 10:00 AM you'd have been out by 10:30 because as a rule tourists (the people who use section K) do not wake up early at all and it's a ghost town. By 11AM or so once the tourists wake up and get there you can't even sit down in that section