I am on a RTW in October starting in NRT. Originally I wanted to stay in NRT for a couple of days before starting the RTW, but plans have changed a bit.

I'll arrive into NRT at 11:45 on an TK flight. My first flight on the RTW is at 15:20. As they are both on different PNR, I am about to change the first flight(s) on the RTW to a late evening flight, so I can deal with normal delays or at least have a chance to rebook my first RTW flight.

At the moment I'm flying OZ103 NRT-ICN connecting to OZ743 ICN-BKK. So my first stopover destination is Bangkok. For the rebooking I am looking at two options. Either a direct flight with NH or TG or a connecting flight via OSA with NH/TG.

Reading the Terms and Conditions I am not really sure if my options (or at least the latter) are considered a change of route which would cost me an additional USD125 or if NRT-BKK is considered a sector so it's for free.

So my basic question is: What is a sector? Any number of connections between stopovers?