Originally Posted by Lux Flyer

Without digging into all the fare rules probably booking code/flight applicability restrictions in the PE fare filings. Searching around what I'm seeing is NH is only making O-available on the UA codeshare flight (G on native flight number, you can use either to get access to the fare) when its combined with a UA US-TYO flight. So theoretically you can search for an O fare, and it looks like it will price PE-PE as an unrestricted mileage fare ($$$).

Though for what you're trying to do, it shouldn't matter, because you can go from Y-J ((unless you really want PE on the TYO-BKK NH flight)) on NH using PlusPoints (PP don't get considered for PE on NH). You just need to be in an applicable booking code, which based on the R discounted fare filings pushing into V or lower, you would need to get an A-fare with UA to get put in an M booking code on the NH flight.