Their service used to be dreadful after Hull closed but everything seemed to change with Covid and I must say I have found their service excellent. Not needed them in the last 3 years as I have a Retirement visa so not sure how things are now. I did wonder whether the positive change was due to a change in Ambassador.
Have u tried Kasikorn in Udon. They, like Udon,s immigration office, are more user friendly and speak English. Lots more Brits living there. I'd try the one in Central first. Good Luck.
and the only queue was the normal queue for the airline check-in. Anticipating congestion, I went through passport control and security earlier than I normally would but sailed through as normal. In fact, quicker than normal.