Just a reminder that immigration offices around the country will be closed on Monday as it’s a substitute holiday for the Constitution day on the 10th.
Also the 29th of December and January 1st are public holidays too.
Generally many offices are super busy after a holiday weekend and are best to be avoided if at all possible.
Land borders are not affected by public holidays.
TLDR : Answer Summary
Immigration offices in Thailand will be closed on Monday due to a substitute holiday for Constitution Day on the 10th. Additional public holidays include December 29th and January 1st. After holiday weekends, immigration offices tend to be busy, so it's best to avoid these times if possible. Note that land borders are not affected by public holidays.