Flying from Bangkok to the United States via South Korea (Incheon): will the passenger be quarantined in South Korea?

Question

If a passenger flies from Bangkok to the United States via South Korea (Incheon), will they be quarantined in South Korea? The passenger is a French citizen and permanent resident of the United States.

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What I have found so far confuses me:

https://www.iatatravelcentre.com/international-travel-document-news/1580226297.htm says:

7. Passengers are subject to quarantine for 14 days and to a PCR test for Coronavirus (COVID-19). [...] They must [...] be tested on Coronavirus (COVID-19) upon arrival. They must stay at designated quarantine facilities for 1 or 2 days until a negative test result is obtained.

Does that apply to transit passengers?

https://www.iatatravelcentre.com/international-travel-document-news/1580226297.htm says:

14. Nationals of Thailand are not allowed to transit if they depart from Thailand or travel onward to Thailand. This does not apply to airline crew.

I don't understand why only nationals of Thailand are not allowed to transit, whereas it sounds that other nationals are allowed. That doesn't make any medical sense (0 new COVID-19 case in Thailand over the past 30 days if we ignore quarantined inbound passengers, and COVID-19 doesn't distinguish nationalities. Maybe genetics at best.). As a result I wonder whether other nationals are truly allowed for transit, in case the ban of nationals of Thailand is just politically motivated.

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Full https://www.iatatravelcentre.com/international-travel-document-news/1580226297.htm in case it changes:

Korea (Rep.) Published 24.06.2020

1. Short-term visas (type C-1 and C-3) issued on or before 5 April are no longer valid.
2. Visa exemptions for 90 nationalities with a normal passport are temporarily suspended.

• This does not apply to airline crew.
• This does not apply to passengers with an APEC Business Travel Card.

3. Korean visas issued by the Wuhan Consulate in the Hubei Province are no longer valid.
4. Visitors who have been in the Hubei Province (China People's Rep.) in the past 14 days are not allowed to transit or enter Korea (Rep.).
5. Nationals of China (People’s Rep.) with a passport issued in the Hubei Province are not allowed to transit or enter Korea (Rep.).
6. Passengers arriving from China (People's Rep) must have a visa issued by Korea (Rep.) to transit through Korea (Rep.).

• This does not apply to nationals of Albania, Andorra, Barbados, Dominica, Guyana, Ireland (Rep.), Korea (Rep.), Malta, Mexico, Monaco, Nicaragua, Palau, San Marino, Slovenia, St. Kitts and Nevis, St. Vincent and the Grenadines, USA, Vatican City (Holy See) and Venezuela.
• This does not apply to passengers with a British passport.
• This does not apply to passengers with a diplomatic, consular, official, service or special passport.

7. Passengers are subject to quarantine for 14 days and to a PCR test for Coronavirus (COVID-19).

• This does not apply to nationals of China (People's Rep.) traveling on business under the Fast Lane program and their accompanying family members. They must:
• self-monitor their health conditions minimum 14 days before departure and hold a medical certificate to prove Coronavirus (COVID-19) negative testing result issued at most 72 hours before departure, and
• be tested on Coronavirus (COVID-19) upon arrival. They must stay at designated quarantine facilities for 1 or 2 days until a negative test result is obtained.

8. Nationals and residents of Korea (Rep.) are required to install 'Self-quarantine safety protection mobile app'.
9. Passengers and airline crew must install 'Self-diagnosis Mobile App' in their personal device and a completed Health Declaration Form and a Special Quarantine Declaration Form must be presented to the quarantine desk upon arrival.
10. All flights must arrive at Incheon International Airport (ICN) between 5:00 and 20:00.
11. Residents of Korea (Rep.) who left Korea (Rep.) after 1 June 2020 must have a Re-Entry Permit and a medical certificate. The certificate must:

• be issued by a local authorized medical institute at most 48 hours before departure; and
• be written in English or Korean; and
• include the date of examination, and the presence or absence of fever, cough, chills, headache, difficulty of breathing, muscle pain and pulmonary symptoms; and
• be signed by a medical examiner.
• This does not apply to passengers with status Diplomats (A-1), Government Officials (A-2, A-3) or Overseas Korean (F-4).

12. Nationals of Mongolia are not allowed to transit if they depart from Mongolia or travel onward to Mongolia.

• This does not apply to airline crew.

13. Nationals of Russian Fed. are not allowed to transit if they depart from Russian Fed. or travel onward to Russian Fed.

• This does not apply to airline crew.

14. Nationals of Thailand are not allowed to transit if they depart from Thailand or travel onward to Thailand.

• This does not apply to airline crew

Answer 1

Per TIMATIC, regarding transit in South Korea:

Admission and Transit Restrictions:

• Passengers arriving from China (People's Rep) must have a visa issued by Korea (Rep.) to transit through Korea (Rep.).

VISA NOT REQUIRED.

Warning:

• Passengers who have been in Bangladesh, Kazakhstan, Kyrgyzstan, Pakistan, Philippines or Uzbekistan in the past 14 days must have a medical certificate with a negative Coronavirus (COVID-19) PCR test result issued at most 48 hours before departure. The certificate must be in English.

• Flights must arrive at Incheon International Airport (ICN) between 5:00 and 20:00.

As such, you're good.