We Raced To Circumnavigate The Globe In 100 Hours

My prediction/ advice (?): 
1. If the Thai flights are missed, both can try and make their way to Athens (can take Wizz Air/Ryanair/Easyjet directly) or to other Greece cities such as Paphos or Thessaloniki and make their way to Athens. (may cost around 60 to 200 USD/2 ppl)
 1a. Then they could take the Scoot Athens-Singapore service.

 1b. Flights to or through Hong Kong, China, Taiwan, or Japan are impossible as border restrictions constrain. For reference, these options are cheaper pre-pandemic and can be wisely used if these borders are fully opened. A stopover through Korea as the border is opened for tourists (not restricted to group tours) will be possible if the video is taken in June. 

  1c(a). There are no direct flights from Thailand or Malaysia to USA/Canada. Flight options from Vietnam are minimal (although possible) and expensive.
  1c(b). From Manila, it is possible to reach Vancouver, San Francisco, or Los Angeles using Philipine Airlines. This is a cheap option costing the players 1600 USD for 2.
  1c(c). From Seoul, it is possible to reach Dallas with just 1200 USD for 2 using American Airlines or Korean Air.
  1c(d). From Singapore, it is possible to reach Vancouver, Seattle, Los Angeles, or San Francisco using Singapore Airlines or United for 1600 USD. 

2. Other options include reaching Abu Dhabi or Jeddah using Wizz Air or Pegasus and could take Air Asia X or Cebu Pacific to Manila or Kuala Lumpur. Alternatively, the route via India is possible with Indian or Middle Eastern budget carriers, through a stopover (visa required), who can continue their journey to South-East Asia. From New Delhi alternatively, both players could take Indian Airlines to Seoul for 800 USD. Singapore could also be reached cheaply from Dubai or India.

If they reach Bangkok using the Thai flight or Singapore using Scoot, connecting to Manila and Singapore is cheap just needing around 90 USD. Connecting to Seoul requires around 350 USD using Air Asia X. 

In order to gain mileage and do challenges through it, I recommend using budget carriers wisely in SE Asian countries between Singapore, Malaysia, Thailand, Philippines, or Indonesia. Flights are extremely cheap like Ryanair in Europe costing a maximum of 80 USD for 2 but the cost of living and transportation is a lot cheaper.