When does the quarantine period officially start during arrival in Thailand?

it starts the next day - the arrival day is called zero and as well the last day.

quarantaine starts the day AFTER you arrive at the hotel ! So day one is the day in which you open your eyes after having your first nights rest

I arrived at about 11:15 PM in Bangkok. Because of a snafu I didn’t get to my hotel till about 1 AM. The day I landed, the previous day, counted as day zero. I don’t know if there’s any official policy that says the day zero begins the day you land on the airport, but that was my experience

Day 0 on arrival

It's consider day 0 when you step into the hotel.

It starts when you reach your hotel, which is just a few hours after you land. There is no real delay in getting you there.

Until you check in to your asq you are mingling with other people, ie; at the airport. So, you do not enter "quarantine" until you get to the hotel. As others have said, 15 nights, leave on 16th day.

Best to arrive at night. If you arrive early and at your ASQ at 6am, that is day 0.

My guess

It starts when you check in

In your guarantine hotel

15 nights - easy. Free the morning after the 15th night

Most off the time they let you out after 14 hole days. If you think you can't do the Quarantine then dont Come before its over

A friend who arrived last month had his flight delayed for several hours, with the result that he arrived in Bangkok well after midnight and didn't arrive at his ASQ hotel until after 5am. They still counted his original scheduled arrival date as day zero, and his quarantine period was not extended by a day.

I would have liked to arrive later in the afternoon. My flight arrived around 11am. Was tired the whole afternoon forcing myself to stay awake.

Would have preferred to get to the hotel later so that I could just crash. But I was also coming from Vancouver Canada. So it was a long journey.

Been there done that..

My plane arrived just after 11pm. I made it through immigration before midnight but was not at the hotel until after midnight. They still counted that as my day 0. I have seen other reports of this same timeline as well. Even with possible delays, the timelines are already set out for your quarantine days at the hotel ahead of time so I don't believe they would change it

The answer is simple when you book your hotel they will give you a date upon the flight time you provided them.

you are free to go 06:00 am that morning on that date they have given you

Day 1 is day after arrival no matter what time you get in.. you must do 15 nights.

Absurd question. Arguing over hours.

The Day you arrive is Day Zero and day 1 is the first full day.

So that makes it total of 16 days and 15 nights

Last day they let me out as soon as clearance paperwork arrived which was about 6 30 am.

Personally i would plan afternoon arrivals even small delay on 11 pm arrival could make you do an extra day.

Not exactly sure when they start counting the days, could be arrive Thailand could be arrival Hotel (quarantine facility ) Hopefully someone who has done a late arrival can clarify