If he wants to, he can. SFO is a legal stopover as domestic gateway in his routing.

Regarding BKK, you may want to evaluate the current ongoing political turmoil in Thailand and weigh if you want to include it in your ticketed itinerary.

Last Dec BKK was underseiged for over a week and travellers were stranded with no way out. Several governments, including Canada and European countries, sent their rescue planes to rescue their nationals. However, US & UK did not do a thing to help their citizens. The situation recently has escalated again. Given there has already been a precedence (airport seige), it could happen again.

Search AA, CX, TG forums on FT on the BKK event you would find horror stories how people tried desperately to leave during the seige.

Personally we purposedly removed BKK from our OW itinerary 2 days before ticketing in December when it looked as if there could be big problem, right before the seige happened - eventhough our travel would be in June.

There are plenty of LCCs fly the intra SE Asia routes at very cheap prices. If you really want to visit BKK or resort islands in Thailand (Puket, Samui, for example), you can easily get cheap tickets to do so but no need to commit yourself in the award itinerary (and left to fend for yourself should something similar happen again).