SAMUI FLIGHTS FOR SANDBOX
The connecting flight on Bangkok Airways must be on an approved sealed route flight. The qualifying sealed route flights are always 4 numbers beginning with "51". Any of the flights you can see for sale on the Bangkok Airways website, such as PG171, are public flights only for domestic passengers. For example, sealed route flights PG5125 and PG5171 flights can only be booked by your international carrier and are not publicly for sale, since they are intended only as sealed route transfer flights for passengers that are arriving in the country and have not been through the Test & Go, Sandbox, or AQ program yet.