ONCE YOU HAVE ARRIVED AT CHAENGWATTANA IMMIGRATION

When you are past the security at the building entrance, you'll be in a large lobby area.The door to Immigration is on the right side.Once you enter that door, you'll be in a small reception type area with people filling out forms, etc Walk through this room and in the next room you'll find the real reception desks where you get a queue number.The 'number' will start with a J or K, areas J and K is where they do the extensions for tourist visas and visa exempt entries.This area is just steps away from reception.As I recall, they process about 50 people each hour. I've arrived at 9 am and received a number as low as J5 and as high as J110. At this time of year, it will likely be busy and will take a few hours. If you arrive after the lunch break, you may be there until they close, they do guarantee to help everyone who has a number and they definitely process more people per hour later in the day.You don't need to sit and wait in the J or K area, you can go downstairs where they have some cafes, etc.to kill the time.Just go back up and check where they are on the numbers every now and then.